From 9de71c84bfc5d6876afdce4b4c4e01bb1bde7b6b Mon Sep 17 00:00:00 2001 From: Simon Forman Date: Fri, 16 Sep 2022 09:03:42 -0700 Subject: [PATCH] Cleaning up docs. Kinda... --- README.md | 20 +- docs/html/FR.html | 2605 ----------------- docs/html/FuncRef.html | 2501 ++++++++++++++++ docs/html/index.html | 20 +- docs/reference/grabN.md | 2 +- docs/reference/mkref/FuncRef.html | 6 +- ...tor-Reference.md => Function-Reference.md} | 2 +- docs/reference/mkref/Makefile | 15 +- 8 files changed, 2535 insertions(+), 2636 deletions(-) delete mode 100644 docs/html/FR.html create mode 100644 docs/html/FuncRef.html rename docs/reference/mkref/{Functor-Reference.md => Function-Reference.md} (99%) diff --git a/README.md b/README.md index be6900c..bae676ddb 100644 --- a/README.md +++ b/README.md @@ -32,14 +32,14 @@ interesting aspects. It's quite a treasure trove. Here is an example of Joy code: - [ [[abs] ii <=] - [ - [<>] [pop !-] || - ] && - ] - [[ !-] [[++]] [[--]] ifte dip] - [[pop !-] [--] [++] ifte ] - ifte + square_spiral ≡ [_p] [_then] [_else] ifte + + _p ≡ [_p0] [_p1] && + _p0 ≡ [abs] ii <= + _p1 ≡ [<>] [pop !-] || + + _then ≡ [ !-] [[++]] [[--]] ifte dip + _else ≡ [pop !-] [--] [++] ifte It might seem unreadable but with a little familiarity it becomes just as legible as any other notation. @@ -97,9 +97,9 @@ coordinate pair in a square spiral (like the kind used to construct an The docs/notebooks dir contains Jupyter notebooks, ... TODO -## Function Reference +### Function Reference -[Function Reference](/FR.html) +[Function Reference](/FuncRef.html) ### Building the Docs diff --git a/docs/html/FR.html b/docs/html/FR.html deleted file mode 100644 index 5828a57..0000000 --- a/docs/html/FR.html +++ /dev/null @@ -1,2605 +0,0 @@ - - - - - - - - -

Version -10.0.0

-

Each function, combinator, or definition should be documented -here.

-
-

&

-

See and.

-
-

&&

-

Combinator

-

Short-circuiting Boolean AND

-

Accept two quoted programs, run the first and expect a Boolean -value, if it's true pop it and run the second program -(which should also return a Boolean value) otherwise pop the second -program (leaving false on the stack.)

-
   [A] [B] &&
----------------- true
-        B
-
-
-   [A] [B] &&
----------------- false
-     false
-
-

Definition

-
nulco [nullary [false]] dip branch
-
-

Derivation

-

TODO: this is derived in one of the notebooks I think, look it -up and link to it, or copy the content here.

-

Discussion

-

This is seldom useful, I suspect, but this way you have it.

-

Crosslinks

-

||

-
-

*

-

See mul.

-
-

•

-

See id.

-
-

^

-

See xor.

-
-

=

-

See eq.

-
-

!=

-

See ne.

-
-

!-

-

Function

-

Not negative.

-
    n !-
------------ n < 0
-   false
-
-
-   n !-
----------- n >= 0
-   true
-
-

Definition

-
0 \>=
-
-

Discussion

-

Return a Boolean value indicating if a number is greater than or -equal to zero.

-
-

>

-

See gt.

-
-

>=

-

See ge.

-
-

>>

-

See rshift.

-
-

-

-

See sub.

-
-

--

-

See pred.

-
-

<

-

See lt.

-
-

<=

-

See le.

-
-

<>

-

See ne.

-
-

\<{}

-

Function

-
   ... a <{}
-----------------
-   ... [] a
-
-

Definition

-
[] swap
-
-

Discussion

-

Tuck an empty list just under the first item on the stack.

-

Crosslinks

-

<<{}

-
-

<<

-

See lshift.

-
-

\<\<{}

-

Function

-
   ... b a <{}
------------------
-   ... [] b a
-
-

Definition

-
[] rollup
-
-

Discussion

-

Tuck an empty list just under the first two items on the -stack.

-

Crosslinks

-

<{}

-
-

%

-

See mod.

-
-

+

-

See add.

-
-

++

-

See succ.

-
-

?

-

Function

-

Is the item on the top of the stack "truthy"?

-

Definition

-
-

dup bool

-
-

Discussion

-

You often want to test the truth value of an item on the stack -without consuming the item.

-

Crosslinks

-

bool

-
-

/

-

See floordiv.

-
-

//

-

See floordiv.

-
-

/floor

-

See floordiv.

-
-

\|\|

-

Combinator

-

Short-circuiting Boolean OR

-

Definition

-
-

nulco [nullary] -dip [true] branch

-
-

Discussion

-

Accept two quoted programs, run the first and expect a Boolean -value, if it’s false pop it and run the second program -(which should also return a Boolean value) otherwise pop the second -program (leaving true on the stack.)

-
   [A] [B] ||
----------------- A -> false
-        B
-
-
-   [A] [B] ||
----------------- A -> true
-      true
-
-

Crosslinks

-

&&

-
-

abs

-

Function

-

Return the absolute value of the argument.

-

Definition

-
-

dup 0 < [] [neg] -branch

-
-
-

add

-

Basis Function

-

Add two numbers together: a + b.

-
-

anamorphism

-

Combinator

-

Build a list of values from a generator program G -and a stopping predicate P.

-
           [P] [G] anamorphism
------------------------------------------
-   [P] [pop []] [G] [dip swons] genrec
-
-

Definition

-
-

[pop []] swap [dip swons] genrec

-
-

Example

-

The range function generates a list of the integers -from 0 to n - 1:

-
-

[0 <=] [-- dup] anamorphism

-
-

Discussion

-

See the Recursion -Combinators notebook.

-
-

and

-

Basis Function

-

Logical bit-wise AND.

-

Crosslinks

-

or xor

-
-

app1

-

"apply one"

-

Combinator

-

Given a quoted program on TOS and anything as the second stack -item run the program without disturbing the stack and replace the -two args with the first result of the program.

-
         ... x [Q] app1
----------------------------------
-   ... [x ...] [Q] infra first
-
-

This is the same effect as the unary -combinator.

-

Definition

-
-

nullary popd

-
-

Discussion

-

Just a specialization of nullary really. Its -parallelizable cousins are more useful.

-

Crosslinks

-

app2 app3 appN unary

-
-

app2

-

Combinator

-

Like app1 with two items.

-
   ... y x [Q] . app2
------------------------------------
-   ... [y ...] [Q] . infra first
-       [x ...] [Q]   infra first
-
-

Definition

-
-

[[grba] [swap] [grba] [swap]] [dip] [[infrst]] [cons] [ii]

-
-

Discussion

-

Unlike app1, which is essentially an alias -for unary, this function is not the same as -binary. Instead of running one program using -exactly two items from the stack and pushing one result (as -binary does) this function takes two items -from the stack and runs the program twice, separately for each of -the items, then puts both results onto the stack.

-

This is not currently implemented as parallel processes but it -can (and should) be done.

-

Crosslinks

-

app1 app3 appN unary

-
-

app3

-

Combinator

-

Like [app1] with three items.

-
     ... z y x [Q] . app3
------------------------------------
-   ... [z ...] [Q] . infra first
-       [y ...] [Q]   infra first
-       [x ...] [Q]   infra first
-
-

Definition

-
-

3 [appN]

-
-

Discussion

-

See [app2].

-

Crosslinks

-

app1 app2 appN unary

-
-

appN

-

Combinator

-

Like [app1] with any number of items.

-
   ... xN ... x2 x1 x0 [Q] n . appN
---------------------------------------
-   ... [xN ...] [Q] . infra first
-                   ...
-       [x2 ...] [Q]   infra first
-       [x1 ...] [Q]   infra first
-       [x0 ...] [Q]   infra first
-
-

Definition

-
-

[[grabN]] [codi] [map] [disenstacken]

-
-

Discussion

-

This function takes a quoted function Q and an -integer and runs the function that many times on that many stack -items. See also [app2].

-

Crosslinks

-

app1 app2 app3 unary

-
-

at

-

See getitem.

-
-

average

-

Function

-

Compute the average of a list of numbers. (Currently broken -until I can figure out what to do about "numeric tower" in -Thun.)

-

Definition

-
-

[[sum]] [[size]] [cleave] [/]

-
-

Discussion

-

Theoretically this function would compute the sum and the size -in two separate threads, then divide. This works but a compiled -version would probably do better to sum and count the list once, in -one thread, eh?

-

As an exercise in Functional Programming in Joy it would be fun -to convert this into a catamorphism. See the Recursion -Combinators notebook.

-
-

b

-

Combinator

-

Run two quoted programs

-
   [P] [Q] b
----------------
-      P Q
-
-

Definition

-
-

[[i]] [dip] [i]

-
-

Discussion

-

This combinator may seem trivial but it comes in handy.

-

Crosslinks

-

dupdip ii

-
-

binary

-

Combinator

-

Run a quoted program using exactly two stack values and leave -the first item of the result on the stack.

-
   ... y x [P] binary
------------------------
-        ... a
-
-

Definition

-
-

[unary] [popd]

-
-

Discussion

-

Runs any other quoted function and returns its first result -while consuming exactly two items from the stack.

-

Crosslinks

-

nullary ternary -unary

-
-

bool

-

Basis Function

-

Convert the item on the top of the stack to a Boolean value.

-

Discussion

-

For integers 0 is false and any other number is -true; for lists the empty list is false -and all other lists are true.

-

Crosslinks

-

[not]

-
-

branch

-

Basis Combinator

-

Use a Boolean value to select and run one of two quoted -programs.

-
   false [F] [T] branch
---------------------------
-          F
-
-   true [F] [T] branch
--------------------------
-             T
-
-

Definition

-
-

[rolldown] [choice] [i]

-
-

Discussion

-

This is one of the fundamental operations (although it can be -defined in terms of [choice] as above). The more common -"if..then..else" construct [ifte] adds a predicate function that is -evaluated [nullary].

-

Crosslinks

-

[choice] [ifte] [select]

-
-

ccccons

-

Function

-
   a b c d [...] ccccons
----------------------------
-       [a b c d ...]
-
-

Do [cons] four times.

-

Definition

-
-

[ccons] [ccons]

-
-

Crosslinks

-

[ccons] [cons] [times]

-
-

ccons

-

Function

-
   a b [...] ccons
----------------------
-      [a b ...]
-
-

Do [cons] two times.

-

Definition

-
-

[cons] [cons]

-
-

Crosslinks

-

[cons] [ccons]

-
-

choice

-

Basis Function

-

Use a Boolean value to select one of two items.

-
   a b false choice
-----------------------
-          a
-
-   a b true choice
----------------------
-          b
-
-

Definition

-
-

[[pop]] [[popd]] [branch]

-
-

Discussion

-

It's a matter of taste whether you implement this in terms of -[branch] or the other way around.

-

Crosslinks

-

[branch] [select]

-
-

clear

-

Basis Function

-

Clear everything from the stack.

-

Definition

-
-

[stack] [bool] [[pop] [stack] [bool]] [loop]

-
-

Crosslinks

-

[stack] [swaack]

-
-

cleave

-

Combinator

-

Run two programs in parallel, consuming one additional item, and -put their results on the stack.

-
   ... x [A] [B] cleave
-------------------------
-        ... a b
-
-

Derivation

-
-

[fork] [popdd]

-
-

Example

-
   1 2 3 [+] [-] cleave
---------------------------
-         1 2 5 -1
-
-

Discussion

-

One of a handful of useful parallel combinators.

-

Crosslinks

-

[clop] [fork] [map]

-
-

clop

-

Combinator

-

Run two programs in parallel, consuming two additional items, -and put their results on the stack.

-
   ... x y [A] [B] clop
---------------------------
-        ... a b
-
-

Definition

-
-

[cleave] [popdd]

-
-

Discussion

-

Like [cleave] but consumes an additional item from the -stack.

-
   1 2 3 4 [+] [-] clop
---------------------------
-         1 2 7 -1
-
-

Crosslinks

-

[cleave] [fork] [map]

-
-

cmp

-

Combinator

-

Take two values and three quoted programs on the stack and run -one of the three depending on the results of comparing the two -values.

-
   a b [G] [E] [L] cmp
-------------------------- a > b
-        G
-
-   a b [G] [E] [L] cmp
-------------------------- a = b
-            E
-
-   a b [G] [E] [L] cmp
-------------------------- a < b
-                L
-
-

Discussion

-

This is useful sometimes, and you can [dup] or [dupd] with two -quoted programs to handle the cases when you just want to deal with -[<=] or [>=] and not all three possibilities, e.g.:

-
[G] [EL] dup cmp
-
-[GE] [L] dupd cmp
-
-

Or even:

-
[GL] [E] over cmp
-
-

Crosslinks

-

TODO: link to tree notebooks where this was used.

-
-

codi

-

Combinator

-

Take a quoted program from the stack, [cons] the next item onto -it, then [dip] the whole thing under what was the third item on the -stack.

-
   a b [F] . codi
---------------------
-         b . F a
-
-

Definition

-
-

[cons] [dip]

-
-

Discussion

-

This is one of those weirdly specific functions that turns out -to be useful in a few places.

-

Crosslinks

-

[appN] [codireco]

-
-

codireco

-

Combinator

-

This is part of the [make_generator] function. You would not use -this combinator directly.

-

Definition

-
-

[codi] [reco]

-
-

Discussion

-

See [make_generator] and the -"Using x to Generate Values" notebook as well as -Recursion -Theory and Joy by Manfred von Thun.

-

Crosslinks

-

[make_generator]

-
-

concat

-

Function

-

Concatinate two lists.

-
   [a b c] [d e f] concat
-----------------------------
-       [a b c d e f]
-
-

Crosslinks

-

[first] [firsttwo] [flatten] [fourth] [getitem] [remove] -[rest] [reverse] [rrest] [second] [shift] [shunt] [size] [sort] -[splitat] [split_list] [swaack] [third] [zip]

-
-

cond

-

Combinator

-

This combinator works like a case statement. It expects a single -quote on the stack that must contain zero or more condition quotes -and a default quote. Each condition quote should contain a quoted -predicate followed by the function expression to run if that -predicate returns true. If no predicates return -true the default function runs.

-
[
-    [ [Predicate0] Function0 ]
-    [ [Predicate1] Function1 ]
-    ...
-    [ [PredicateN] FunctionN ]
-    [Default]
-]
-cond
-
-

Discussion

-

It works by rewriting into a chain of nested [ifte]{.title-ref} -expressions, e.g.:

-
      [[[B0] T0] [[B1] T1] [D]] cond
------------------------------------------
-   [B0] [T0] [[B1] [T1] [D] ifte] ifte
-
-

Crosslinks

-

[ifte]

-
-

cons

-

Basis Function

-

Given an item and a list, append the item to the list to make a -new list.

-
   a [...] cons
-------------------
-     [a ...]
-
-

Discussion

-

Cons is a venerable old function -from Lisp. Its inverse operation is [uncons].

-

Crosslinks

-

[uncons]

-
-

dinfrirst

-

Combinator

-

Specialist function (that means I forgot what it does and -why.)

-

Definition

-
-

[dip] [infrst]

-
-
-

dip

-

Basis Combinator

-

The dip combinator expects a quoted program on the -stack and below it some item, it hoists the item into the -expression and runs the program on the rest of the stack.

-
   ... x [Q] . dip
----------------------
-         ... . Q x
-
-

Discussion

-

This along with [infra] are enough to update any datastructure. -See the "Traversing -Datastructures with Zippers" notebook.

-

Note that the item that was on the top of the stack -(x in the example above) will not be treated specially -by the interpreter when it is reached again. This is something of a -footgun. My advice is to avoid putting bare unquoted symbols onto -the stack, but then you can't use symbols as "atoms" and also use -dip and infra to operate on compound -datastructures with atoms in them. This is a kind of side-effect of -the Continuation-Passing Style. The dip combinator -could "set aside" the item and replace it after running -Q but that means that there is an "extra space" where -the item resides while Q runs. One of the nice things -about CPS is that the whole state is recorded in the stack and -pending expression (not counting modifications to the -dictionary.)

-

Crosslinks

-

[dipd] [dipdd] [dupdip] [dupdipd] [infra]

-
-

dipd

-

Combinator

-

Like [dip] but expects two items.

-
   ... y x [Q] . dipd
--------------------------
-           ... . Q y x
-
-

Discussion

-

See [dip].

-

Crosslinks

-

[dip] [dipdd] [dupdip] [dupdipd] [infra]

-
-

dipdd

-

Combinator

-

Like [dip] but expects three items. :

-
   ... z y x [Q] . dip
------------------------------
-             ... . Q z y x
-
-

Discussion

-

See [dip].

-

Crosslinks

-

[dip] [dipd] [dupdip] [dupdipd] [infra]

-
-

disenstacken

-

Function

-

The disenstacken function expects a list on top of -the stack and makes that the stack discarding the rest of the -stack.

-
   1 2 3 [4 5 6] disenstacken
---------------------------------
-            6 5 4
-
-

Definition

-
-

[[clear]] [dip] [reverse] unstack

-
-

Discussion

-

Note that the order of the list is not changed, it just looks -that way because the stack is printed with the top on the right -while lists are printed with the top or head on the left.

-

Crosslinks

-

[enstacken] [stack] unstack

-
-

div

-

See floordiv.

-
-

divmod

-

Function

-
    x y divmod
-------------------
-     q      r
-   (x/y)  (x%y)
-
-

Invariant: qy + r = x.

-

Definition

-
-

[[floordiv]] [[mod]] [clop]

-
-
-

downtozero

-

Function

-

Given a number greater than zero put all the Natural numbers -(including zero) less than that onto the stack.

-

Example

-
   3 down_to_zero
---------------------
-      3 2 1 0
-
-

Definition

-
-

[0 >] [[dup] [--]] [while]

-
-

Crosslinks

-

[range]

-
-

drop

-

Function

-

Expects an integer and a quote on the stack and returns the -quote with n items removed off the top.

-

Example

-
   [a b c d] 2 drop
-----------------------
-       [c d]
-
-

Definition

-
-

[[rest]] [times]

-
-

Crosslinks

-

[take]

-
-

dup

-

Basis Function

-

"Dup"licate the top item on the stack.

-
   a dup
------------
-    a a
-
-

Crosslinks

-

[dupd] [dupdd] [dupdip] [dupdipd]

-
-

dupd

-

Function

-

[dup] the second item down on the stack.

-
   a b dupd
---------------
-    a a b
-
-

Definition

-
-

[[dup]] [dip]

-
-

Crosslinks

-

[dup] [dupdd] [dupdip] [dupdipd]

-
-

dupdd

-

Function

-

[dup] the third item down on the stack.

-
   a b c dupdd
------------------
-     a a b c
-
-

Definition

-
-

[[dup]] [dipd]

-
-

Crosslinks

-

[dup] [dupd] [dupdip] [dupdipd]

-
-

dupdip

-

Combinator

-

Apply a function F and [dup] the item under it on -the stack.

-
   a [F] dupdip
-------------------
-      a F a
-
-

Definition

-
-

[dupd] [dip]

-
-

Derivation

-
a [F] dupdip
-a [F] dupd dip
-a [F] [dup] dip dip
-a dup [F] dip
-a a [F] dip
-a F a
-
-

Discussion

-

A very common and useful combinator.

-

Crosslinks

-

[dupdipd]

-
-

dupdipd

-

Combinator

-

Run a copy of program F under the next item down on -the stack.

-
   a [F] dupdipd
--------------------
-      F a [F]
-
-

Definition

-
-

[dup] [dipd]

-
-

Crosslinks

-

[dupdip]

-
-

enstacken

-

Function

-

Put the stack onto the stack replacing the contents of the -stack.

-
   ... a b c enstacken
--------------------------
-       [c b a ...]
-
-

Definition

-
-

[stack] [[clear]] [dip]

-
-

Discussion

-

This is a destructive version of [stack]. See the note under -[disenstacken] about the apparent but illusory reversal of the -stack.

-

Crosslinks

-

[stack] [unstack] [disenstacken]

-
-

eq

-

Basis Function

-

Compare the two items on the top of the stack for equality and -replace them with a Boolean value.

-
   a b eq
--------------
-   Boolean
-   (a = b)
-
-

Crosslinks

-

[cmp] [ge] [gt] [le] [lt] [ne]

-
-

first

-

Function

-

Replace a list with its first item.

-
   [a ...]
---------------
-      a
-
-

Definition

-
-

[uncons] [pop]

-
-

Crosslinks

-

[second] [third] [fourth] [rest]

-
-

first_two

-

Function

-

Replace a list with its first two items.

-
   [a b ...] first_two
--------------------------
-           a b
-
-

Definition

-
-

[uncons] [first]

-
-

Crosslinks

-

[first] [second] [third] [fourth] [rest]

-
-

flatten

-

Function

-

Given a list of lists, concatinate them.

-

Example

-
   [[1 2] [3 [4] 5] [6 7]] flatten
--------------------------------------
-          [1 2 3 [4] 5 6 7]
-
-

Definition

-
-

[\<{}] [[concat]] [step]

-
-

Discussion

-

Note that only one "level" of lists is flattened. In the example -above [4] is not unquoted.

-

Crosslinks

-

[concat] [first] [firsttwo] [fourth] [getitem] [remove] -[rest] [reverse] [rrest] [second] [shift] [shunt] [size] [sort] -[splitat] [split_list] [swaack] [third] [zip]

-
-

floor

-

Basis Function

-

Return the largest integer \<= x.

-

Discussion

-

This function doesn't make sense (yet) to have because there are -(as yet) only integers in the system.

-
-

floordiv

-

Basis Function

-

I don't know why this is called "floor" div, I think it rounds -its result down (not towards zero or up.)

-
   a b floordiv
-------------------
-      (a/b)
-
-

Discussion

-

All the division commands need to be revisited when the "numeric -tower" for Thun gets nailed down.

-

Crosslinks

-

[divmod]

-
-

fork

-

Combinator

-

Run two quoted programs in parallel and replace them with their -results.

-
   ... [F] [G] fork
-----------------------
-       ... f g
-
-

Definition

-
-

[[i]] [app2]

-
-

Discussion

-

The basic parallelism combinator, the two programs are run -independently.

-

Crosslinks

-

[cleave] [clop] [map]

-
-

fourth

-

Function

-

Replace a list with its fourth item.

-
   [a b c d ...] fourth
---------------------------
-          d
-
-

Definition

-
-

[rest] [third]

-
-

Crosslinks

-

[first] [second] [third] [rest]

-
-

gcd

-

Function

-

Take two integers from the stack and replace them with their -Greatest Common Denominator.

-

Definition

-
-

true [[tuck] [mod] [dup] 0 [>]] [loop] [pop]

-
-

Discussion

-

Euclid's Algorithm

-
-

gcd2

-

Function

-

Compiled GCD function.

-

Discussion

-

See [gcd].

-

Crosslinks

-

[gcd]

-
-

ge

-

Basis Function

-

Greater-than-or-equal-to comparison of two numbers.

-
   a b ge
---------------
-   Boolean
-   (a >= b)
-
-

Crosslinks

-

[cmp] [eq] [gt] [le] [lt] [ne]

-
-

genrec

-

Combinator

-

General Recursion -Combinator.

-
                      [if] [then] [rec1] [rec2] genrec
----------------------------------------------------------------------
-   [if] [then] [rec1 [[if] [then] [rec1] [rec2] genrec] rec2] ifte
-
-

Definition

-
-

[[[genrec]] [ccccons]] [nullary] [swons] [concat] [ifte]

-
-

(Note that this definition includes the genrec -symbol itself, it is self-referential. This is possible because the -definition machinery does not check that symbols in defs are in the -dictionary. genrec is the only self-referential -definition.)

-

Discussion

-

See the Recursion -Combinators notebook.

-

From "Recursion -Theory and Joy" by Manfred von Thun:

-
-

"The genrec combinator takes four program parameters in addition -to whatever data parameters it needs. Fourth from the top is an -if-part, followed by a then-part. If the if-part yields true, then -the then-part is executed and the combinator terminates. The other -two parameters are the rec1-part and the rec2-part. If the if-part -yields false, the rec1-part is executed. Following that the four -program parameters and the combinator are again pushed onto the -stack bundled up in a quoted form. Then the rec2-part is executed, -where it will find the bundled form. Typically it will then execute -the bundled form, either with i or with app2, or some other -combinator."

-
-

The way to design one of these is to fix your base case -[then] and the test [if], and then treat -rec1 and rec2 as an else-part -"sandwiching" a quotation of the whole function.

-

For example, given a (general recursive) function -F:

-
F == [I] [T] [R1] [R2] genrec
-
-

If the [I] if-part fails you must derive -R1 and R2 from: :

-
... R1 [F] R2
-
-

Just set the stack arguments in front, and figure out what -R1 and R2 have to do to apply the quoted -[F] in the proper way. In effect, the -genrec combinator turns into an [ifte] combinator with -a quoted copy of the original definition in the else-part:

-
F == [I] [T] [R1]   [R2] genrec
-  == [I] [T] [R1 [F] R2] ifte
-
-

Tail recursive functions are those where R2 is the -i combinator:

-
P == [I] [T] [R] tailrec
-  == [I] [T] [R [P] i] ifte
-  == [I] [T] [R P] ifte
-
-

Crosslinks

-

[anamorphism] [tailrec] [x]

-
-

getitem

-

Function

-

Expects an integer and a quote on the stack and returns the item -at the nth position in the quote counting from 0.

-

Example

-
   [a b c d] 2 getitem
--------------------------
-        c
-
-

Definition

-
-

[drop] [first]

-
-

Discussion

-

If the number isn't a valid index into the quote -getitem will cause some sort of problem (the exact -nature of which is implementation-dependant.)

-

Crosslinks

-

[concat] [first] [firsttwo] [flatten] [fourth] [remove] -[rest] [reverse] [rrest] [second] [shift] [shunt] [size] [sort] -[splitat] [split_list] [swaack] [third] [zip]

-
-

grabN

-

Function

-

Expect a number on the top of the satck and put that many items -from uner it onto a new list.

-

Example

-
   a b c d e 3 grabN
------------------------
-      a b [c d e]
-
-

Definition

-
-

[\<{}] [[cons]] [times]

-
-
-

grba

-

Function

-

A weird function used in [app2] that does this:

-
      ... 1 2 3 4 5 grba
--------------------------------
-   ... 1 2 3 [4 3 2 1 ...] 5
-
-

It grabs the stack under the top item, and substitutes it for -the second item down on the stack.

-

Definition

-
-

[[stack] [popd]] [dip]

-
-

Discussion

-

This function "grabs" an item from the stack along with a copy -of the stack. It's part of the [app2] definition.

-

Crosslinks

-

[app2]

-
-

gt

-

Basis Function

-

Greater-than comparison of two numbers.

-
   a b gt
---------------
-   Boolean
-   (a > b)
-
-

Crosslinks

-

[cmp] [eq] [ge] [le] [lt] [ne]

-
-

help

-

Function

-

Accepts a quoted symbol on the top of the stack and prints its -documentation.

-
   [foo] help
-----------------
-
-

Discussion

-

Technically this is equivalent to pop, but it will -only work if the item on the top of the stack is a quoted -symbol.

-
-

hypot

-

Function

-
         x y hypot
----------------------------
-   sqrt(sqr(x) + sqr(y))
-
-

Definition

-
-

[[sqr]] [ii] [+] [sqrt]

-
-

Discussion

-

This is another function that has to wait on the numeric -tower.

-

Crosslinks

-

[sqrt]

-
-

i

-

Basis Combinator

-

Append a quoted expression onto the pending expression.

-
   [Q] . i
--------------
-       . Q
-
-

Discussion

-

This is a fundamental combinator. It is used in all kinds of -places. For example, the [x] combinator can be defined as dup -i.

-
-

id

-

Basis Function

-

The identity function.

-

Discussion

-

Does nothing. It's kind of a mathematical thing, but it -occasionally comes in handy.

-
-

ifte

-

Combinator

-

If-Then-Else combinator, a common and convenient specialization -of [branch].

-
        [if] [then] [else] ifte
----------------------------------------
-   [if] nullary [else] [then] branch
-
-

Definition

-
-

[[nullary]] [dipd] [swap] [branch]

-
-

Crosslinks

-

[branch] [loop] [while]

-
-

ii

-

Combinator

-

Take a quoted program from the stack and run it twice, first -under the top item, then again with the top item.

-
... a [Q] ii
-------------------
- ... Q a Q
-
-

Definition

-
-

[[dip]] [dupdip] [i]

-
-

Example

-

It's a little tricky to understand how this works so here's an -example trace:

-
      1 2 3 4 [++] • [dip] dupdip i
-1 2 3 4 [++] [dip] • dupdip i
-      1 2 3 4 [++] • dip [++] i
-             1 2 3 • ++ 4 [++] i
-             1 2 4 • 4 [++] i
-           1 2 4 4 • [++] i
-      1 2 4 4 [++] • i
-           1 2 4 4 • ++
-           1 2 4 5 •
-
-

Discussion

-

In some cases (like the example above) this is the same effect -as using [app2] but most of the time it's not:

-
   1 2 3 4 [+] ii
---------------------
-        1 9
-
-   1 2 3 4 [+] app2
-----------------------
-       1 2 5 6
-
-

Crosslinks

-

[app2] [b]

-
-

infra

-

Combinator

-

Accept a quoted program and a list on the stack and run the -program with the list as its stack. Does not affect the stack -(below the list.)

-
   ... x y z [a b c] [Q] infra
----------------------------------
-    c b a Q [z y x ...] swaack
-
-

Definition

-
-

[swons] [swaack] [[i]] [dip] [swaack]

-
-

Discussion

-

This is one of the more useful combinators. It allows a quoted -expression to serve as a stack for a program, effectively running -it in a kind of "pocket universe". If the list represents a -datastructure then infra lets you work on its internal -structure.

-

Crosslinks

-

swaack

-
-

infrst

-

Combinator

-

Does [infra] and then extracts the [first] item from the -resulting list.

-

Definition

-
-

[infra] [first]

-
-
-

inscribe

-

Create a new Joy function definition in the Joy dictionary. A -definition is given as a quote with a name followed by a Joy -expression.

-

Example

-
[sqr dup mul] inscribe
-
-

Discussion

-

This is the only function that modifies the dictionary. It's -provided as a convenience, for tinkering with new definitions -before entering them into the defs.txt file. It can be -abused, which you should avoid unless you know what you're -doing.

-
-

le

-

Basis Function

-

Less-Than-or-Equal-to comparison of the two items on the top of -the stack, replacing them with a Boolean value.

-
   a b le
--------------
-   Boolean
-   (a <= b)
-
-

Crosslinks

-

[cmp] [eq] [ge] [gt] [lt] [ne]

-
-

loop

-

Basis Combinator

-

Expect a quoted program Q and a Boolean value on -the stack. If the value is false discard the quoted program, -otherwise run a copy of Q and loop -again.

-
   false [Q] loop
---------------------
-
-
-   true [Q] . loop
---------------------------
-            . Q [Q] loop
-
-

Discussion

-

This, along with [branch] and [fork], is one of the four main -combinators of all programming. The fourth, sequence, is implied by -juxtaposition. That is to say, in Joy F G is like -G(F(...)) in a language bassed on function -application. Or again, to quote the Joy -Wikipedia entry#Mathematical_purity),

-
-

In Joy, the meaning function is a homomorphism from the -syntactic monoid onto the semantic monoid. That is, the syntactic -relation of concatenation of symbols maps directly onto the -semantic relation of composition of functions.

-
-

Anyway, [branch], [fork], amd [loop] are the fundamental -combinators in Joy. Just as [branch] has it's more common and -convenient form [ifte], [loop] has [while].

-

Crosslinks

-

[branch] [fork] [while]

-
-

lshift

-

Basis Function

-

Logical -Left-Shift

-
   a n lshift
-----------------
-     (a×2ⁿ)
-
-

Crosslinks

-

[rshift]

-
-

lt

-

Basis Function

-

Less-Than comparison of the two items on the top of the stack, -replacing them with a Boolean value.

-
   a b lt
--------------
-   Boolean
-   (a < b)
-
-

Crosslinks

-

[cmp] [eq] [ge] [gt] [le] [ne]

-
-

make_generator

-

Function

-

Given an initial state value and a quoted generator function -build a generator quote.

-
   state [generator function] make_generator
------------------------------------------------
-     [state [generator function] codireco]
-
-

Example

-
   230 [dup ++] make_generator
----------------------------------
-     [230 [dup ++] codireco]
-
-

And then:

-
   [230 [dup ++] codireco] 5 [x] times pop
----------------------------------------------
-             230 231 232 233 234
-
-

Definition

-
-

[[codireco]] [ccons]

-
-

Discussion

-

See the -"Using x to Generate Values" notebook.

-

Crosslinks

-

[codireco]

-
-

map

-

Combinator

-

Given a list of items and a quoted program run the program for -each item in the list (with the rest of the stack) and replace the -old list and the program with a list of the results.

-

Example

-
   5 [1 2 3] [++ *] map
---------------------------
-       5 [10 15 20]
-
-

Discussion

-

This is a common operation in many languages. In Joy it can be a -parallelism combinator due to the "pure" nature of the -language.

-

Crosslinks

-

[app1] [app2] [app3] appN [fork]

-
-

max

-

Basis Function

-

Given a list find the maximum.

-

Example

-
   [1 2 3 4] max
--------------------
-         4
-
-

Crosslinks

-

[min] [size] [sum]

-
-

min

-

Basis Function

-

Given a list find the minimum.

-

Example

-
   [1 2 3 4] min
--------------------
-         1
-
-

Crosslinks

-

[max] [size] [sum]

-
-

mod

-

Basis Function

-

Return the remainder of a divided by -b.

-
   a b mod
--------------
-    (a%b)
-
-

Crosslinks

-

[divmod] [mul]

-
-

modulus

-

See mod.

-
-

mul

-

Basis Function

-

Multiply two numbers.

-
   a b mul
--------------
-    (a×b)
-
-

Crosslinks

-

[div] [product]

-
-

ne

-

Basis Function

-

Not-Equal comparison of the two items on the top of the stack, -replacing them with a Boolean value.

-
   a b ne
--------------
-   Boolean
-   (a = b)
-
-

Crosslinks

-

[cmp] [eq] [ge] [gt] [le] [lt]

-
-

neg

-

Function

-

Invert the sign of a number.

-
   a neg
------------
-    -a
-
-

Definition

-
-

0 [swap] [-]

-
-
-

not

-

Function

-

Like [bool] but convert the item on the top of the stack to the -inverse Boolean value.

-
   true not
---------------
-    false
-
-   false not
----------------
-     true
-
-

Definition

-
-

[bool] [true] [false] [branch]

-
-

Crosslinks

-

[bool]

-
-

nulco

-

Function

-

Take the item on the top of the stack and [cons] it onto -[nullary].

-
     [F] nulco
--------------------
-   [[F] nullary]
-
-

Definition

-
-

[[nullary]] [cons]

-
-

Discussion

-

Helper function for [\|\|] and [&&].

-

Crosslinks

-

[&&] [\|\|]

-
-

nullary

-

Combinator

-

Run a quoted program without using any stack values and leave -the first item of the result on the stack.

-
   ... [P] nullary
----------------------
-        ... a
-
-

Definition

-
-

[[stack]] [dip] [infra] [first]

-
-

Example

-
... [P] nullary
-... [P] [stack] dip infra first
-... stack [P] infra first
-... [...] [P] infra first
-... [a ...] first
-...  a
-
-

Discussion

-

A very useful function that runs any other quoted function and -returns it's first result without disturbing the stack (under the -quoted program.)

-

Crosslinks

-

unary binary ternary

-
-

of

-

Function

-

Like [getitem] but [swap]s the order of arguments.

-

Example

-
   2 [a b c d] of
---------------------
-         c
-
-

Definition

-
-

[swap] [getitem]

-
-

Crosslinks

-

[getitem]

-
-

or

-

Basis Function

-

Logical bit-wise OR.

-

Crosslinks

-

[and] [xor]

-
-

over

-

Function

-

[dup] the second item on the stack over the -first.

-
   a b over
---------------
-    a b a
-
-

Definition

-

There are many many ways to define this function.

-
-

[swap] [tuck]

-

[[pop]] [nullary]

-

[[dup]] [dip] [swap]

-

[unit] [dupdip]

-

[unit] [dupdipd] [first]

-
-

And so on...

-

Discussion

-

A fine old word from Forth.

-

Crosslinks

-

[tuck]

-
-

pam

-

Combinator

-

Take a list of quoted functions from the stack and replace it -with a list of the [first] results from running those functions (on -copies of the rest of the stack.)

-

Example

-
   5 7 [[+][-][*][/][%]] pam
--------------------------------
-      5 7 [12 -2 35 0 5]
-
-

Definition

-
-

[[i]] [map]

-
-

Discussion

-

A specialization of [map] that runs a list of functions in -parallel (if the underlying [map] function is so implemented, of -course.)

-

Crosslinks

-

[map]

-
-

pick

-

See getitem.

-
-

pm

-

Function

-

Plus or minus. Replace two numbers with their sum and -difference.

-
      a b pm
------------------
-   (a+b) (a-b)
-
-

Definition

-
-

[+] [-] [clop]

-
-
-

pop

-

Basis Function

-

Pop the top item from the stack and discard it.

-
   a pop
------------
-
-

Crosslinks

-

[popd] [popdd] [popop] [popopd] [popopdd] [popopop]

-
-

popd

-

Function

-

[pop] the second item down on the stack.

-
   a b popd
---------------
-      b
-
-

Definition

-
-

[swap] [pop]

-
-

Crosslinks

-

[pop] [popdd] [popop] [popopd] [popopdd] [popopop]

-
-

popdd

-

Function

-

[pop] the third item on the stack.

-
   a b c popdd
------------------
-       b c
-
-

Definition

-
-

[rolldown] [pop]

-
-

Crosslinks

-

[pop] [popd] [popop] [popopd] [popopdd] [popopop]

-
-

popop

-

Function

-

[pop] two items from the stack.

-
   a b popop
----------------
-
-

Definition

-
-

[pop] [pop]

-
-

Crosslinks

-

[pop] [popd] [popdd] [popopd] [popopdd] [popopop]

-
-

popopd

-

Function

-

[pop] the second and third items from the stack.

-
   a b c popopd
-------------------
-        c
-
-

Definition

-
-

[rollup] [popop]

-
-

Crosslinks

-

[pop] [popd] [popdd] [popop] [popopdd] [popopop]

-
-

popopdd

-

Function

-
   a b c d popopdd
----------------------
-        c d
-
-

Definition

-
-

[[popop]] [dipd]

-
-

Crosslinks

-

[pop] [popd] [popdd] [popop] [popopd] [popopop]

-
-

popopop

-

Function

-

[pop] three items from the stack.

-
   a b c popopop
--------------------
-
-

Definition

-
-

[pop] [popop]

-
-

Crosslinks

-

[pop] [popd] [popdd] [popop] [popopd] [popopdd]

-
-

pow

-

Basis Function

-

Take two numbers a and b from the -stack and raise a to the nth power. -(b is on the top of the stack.)

-
   a n pow
--------------
-    (aⁿ)
-
-

Example

-
   2 [2 3 4 5 6 7 8 9] [pow] map
------------------------------------
-    2 [4 8 16 32 64 128 256 512]
-
-
-

pred

-

Function

-

Predecessor. Decrement TOS.

-

Definition

-
-

1 -

-
-

Crosslinks

-

[succ]

-
-

primrec

-

Combinator

-

From the "Overview -of the language JOY"

-
-

The primrec combinator expects two quoted programs in addition -to a data parameter. For an integer data parameter it works like -this: If the data parameter is zero, then the first quotation has -to produce the value to be returned. If the data parameter is -positive then the second has to combine the data parameter with the -result of applying the function to its predecessor.

-

5 [1] [*] primrec

-

Then primrec tests whether the top element on the stack -(initially the 5) is equal to zero. If it is, it pops it off and -executes one of the quotations, the [1] which leaves 1 on the stack -as the result. Otherwise it pushes a decremented copy of the top -element and recurses. On the way back from the recursion it uses -the other quotation, [*], to multiply what is now a factorial on -top of the stack by the second element on the stack.

-
-
   0 [Base] [Recur] primrec
-------------------------------
-      Base
-
-         n [Base] [Recur] primrec
------------------------------------------- n > 0
-   n (n-1) [Base] [Recur] primrec Recur
-
-

Discussion

-

Simple and useful specialization of the [genrec] combinator from -the original -Joy system.

-

Crosslinks

-

[genrec] [tailrec]

-
-

product

-

Function

-

Just as [sum] sums a list of numbers, this function multiplies -them together.

-

Definition

-
-

1 [swap] [[mul]] [step]

-
-

Or,

-
-

[1] [[mul]] [primrec]

-
-
-

quoted

-

Function

-

"Quote D" Wrap the second item on the stack in a list.

-
   a b quoted
-----------------
-     [a] b
-
-

Definition

-
-

[[unit]] [dip]

-
-

Discussion

-

This comes from the original Joy stuff.

-

Crosslinks

-

[unit]

-
-

range

-

Function

-

Expect a number n on the stack and replace it with -a list: [(n-1)...0].

-

Example

-
     5 range
------------------
-   [4 3 2 1 0]
-
-   -5 range
---------------
-      []
-
-

Definition

-
-

[0 \<=] [1 - [dup]] [anamorphism]

-
-

Discussion

-

If n is less than 1 the resulting list is -empty.

-

Crosslinks

-

[rangetozero]

-
-

rangetozero

-

Function

-

Take a number n from the stack and replace it with -a list [0...n].

-

Example

-
   5 range_to_zero
----------------------
-    [0 1 2 3 4 5]
-
-

Definition

-
-

[unit] [[downtozero]] [infra]

-
-

Discussion

-

Note that the order is reversed compared to [range].

-

Crosslinks

-

[downtozero] [range]

-
-

reco

-

Function

-

Replace the first item in a list with the item under it.

-
   a [b ...] reco
---------------------
-     [a ...]
-
-

Definition

-
-

[rest] [cons]

-
-

Crosslinks

-

[codireco] [make_generator]

-
-

rem

-

See mod.

-
-

remainder

-

See mod.

-
-

remove

-

Function

-

Expects an item on the stack and a quote under it and removes -that item from the the quote. The item is only removed once. If the -list is empty or the item isn't in the list then the list is -unchanged.

-
   [1 2 3 1] 1 remove
-------------------------
-        [2 3 1]
-
-

Definition

-

See the -"Remove Function" notebook.

-
-

rest

-

Basis Function

-
   [a ...] rest
-------------------
-      [...]
-
-

Crosslinks

-

[first] [uncons]

-
-

reverse

-

Function

-

Reverse the list on the top of the stack.

-

Example

-
   [1 2 3] reverse
----------------------
-       [3 2 1]
-
-

Definition

-
-

[\<{}] [shunt]

-
-
-

rolldown

-

Function

-
   a b c rolldown
---------------------
-       b c a
-
-

Definition

-
-

[swapd] [swap]

-
-

Crosslinks

-

[rollup]

-
-

rollup

-

Function

-
   a b c rollup
-------------------
-      c a b
-
-

Definition

-
-

[swap] [swapd]

-
-

Crosslinks

-

[rolldown]

-
-

roll>

-

See rollup.

-
-

roll<

-

See rolldown.

-
-

round

-

Function

-

Round a number to a given precision in decimal digits.

-

Discussion

-

Another one that won't make sense until the "numeric tower" is -nailed down.

-
-

rrest

-

Function

-
   [a b ...] rrest
----------------------
-        [...]
-
-

Definition

-
-

[rest] [rest]

-
-

Crosslinks

-

[rest]

-
-

rshift

-

Basis Function

-

Logical -Right-Shift

-
   a n rshift
-----------------
-     (a∕2ⁿ)
-
-

Crosslinks

-

[lshift]

-
-

run

-

Function

-

Run a quoted program in a list.

-

Example

-
   [1 2 +] run
------------------
-       [3]
-
-

Definition

-
-

[\<{}] [infra]

-
-
-

second

-

Function

-
   [a b ...] second
-----------------------
-          b
-
-

Definition

-
-

[rest] [first]

-
-

Crosslinks

-

[first] [third] [fourth]

-
-

select

-

Basis Function

-

Use a Boolean value to select one of two items from a sequence. -:

-
   [a b] false select
-------------------------
-           a
-
-   [a b] true select
------------------------
-           b
-
-

Discussion

-

The sequence can contain more than two items but not fewer.

-

Crosslinks

-

[choice]

-
-

sharing

-

Function

-

Print redistribution information.

-

Discussion

-

Mathematically this is a form of [id], but it has the -side-effect of printing out the GPL notice.

-

Crosslinks

-

[warranty]

-
-

shift

-

Function

-

Move the top item from one list to another.

-

Example

-
   [x y z] [a b c] shift
----------------------------
-      [a x y z] [b c]
-
-

Definition

-
-

[uncons] [[swons]] [dip]

-
-

Crosslinks

-

[shunt]

-
-

shunt

-

Function

-

Like [concat] but [reverse] the top list into the second.

-

Example

-
   [a b c] [d e f] shunt
----------------------------
-       [f e d a b c]
-
-

Definition

-
-

[[swons]] [step]

-
-

Discussion

-

This is more efficient than [concat] so prefer it if you don't -need to preserve order.

-

Crosslinks

-

[concat] [reverse] [shift]

-
-

size

-

Function

-

Replace a list with its size.

-

Example

-
   [23 [cats] 4] size
-------------------------
-           3
-
-

Definition

-
-

[[pop] [++]] [step_zero]

-
-
-

sort

-

Function

-

Given a list return it sorted.

-

Example

-
   [4 2 5 7 1] sort
-----------------------
-      [1 2 4 5 7]
-
-
-

spiral_next

-

Function

-

Example code.

-

Discussion

-

See the "Square Spiral -Example Joy Code" notebook.

-
-

split_at

-

Function

-

Split a list (second on the stack) at the position given by the -number on the top of the stack.

-

Example

-
   [1 2 3 4 5 6 7] 4 split_at
---------------------------------
-       [5 6 7] [4 3 2 1]
-
-

Definition

-
-

[[drop]] [[take]] [clop]

-
-

Discussion

-

Take a list and a number n from the stack, take -n items from the top of the list and [shunt] them onto -a new list that replaces the number n on the top of -the stack.

-

Crosslinks

-

[split_list]

-
-

split_list

-

Function

-

Split a list (second on the stack) at the position given by the -number on the top of the stack such that [concat] would reconstruct -the original list.

-
   [1 2 3 4 5 6 7] 4 split_list
-----------------------------------
-        [1 2 3 4] [5 6 7]
-
-

Definition

-
-

[[take] [reverse]] [[drop]] [clop]

-
-

Discussion

-

Compare with [split_at]. This function does extra work to ensure -that [concat] would reconstruct the original list.

-

Crosslinks

-

[split_at]

-
-

sqr

-

Function

-

Square the number on the top of the stack.

-
   n  sqr
-------------
-     n²
-
-

Definition

-
-

[dup] [mul]

-
-
-

sqrt

-

Basis Function Combinator

-

Return the square root of the number a. Negative numbers return -complex roots.

-

Discussion

-

Another "numeric tower" hatch...

-
-

stack

-

Function

-

Put the stack onto the stack.

-
      ... c b a stack
----------------------------
-   ... c b a [a b c ...]
-
-

Definition

-
-

[] [swaack] [dup] [swaack] [first]

-
-

Discussion

-

This function forms a pair with [unstack], and together they -form the complement to the "destructive" pair [enstacken] and -[disenstacken].

-

Crosslinks

-

[unstack] [enstacken] [disenstacken]

-
-

stackd

-

Function

-

Grab the stack under the top item and put it onto the stack.

-

Example

-
   ... 1 2 3 stackd
-------------------------
-  ... 1 2 [2 1 ...] 3
-
-

Definition

-
-

[[stack]] [dip]

-
-
-

step

-

Combinator

-

Run a quoted program on each item in a sequence.

-
   ... [] [Q] step
----------------------
-         ...
-
-
-   ... [a] [Q] step
-----------------------
-      ... a Q
-
-
-   ... [a b c] [Q] . step
-----------------------------------------
-             ... a . Q [b c] [Q] step
-
-

Discussion

-

See the Recursion -Combinators notebook.

-

Crosslinks

-

[step_zero]

-
-

step_zero

-

Combinator

-

Like [step] but with 0 as the initial value.

-
   [...] [F] step_zero
--------------------------
-     0 [...] [F] step
-
-

Definition

-
-

0 [roll>] [step]

-
-

Discussion

-

[size] and [sum] can both be defined in terms of this -specialization of [step].

-

Crosslinks

-

[step]

-
-

stuncons

-

Function

-

Take the [stack] and [uncons] the top item.

-

Example

-
   1 2 3 stuncons
---------------------
-   1 2 3 3 [2 1]
-
-

Definition

-
-

[stack] [uncons]

-
-
-

stununcons

-

Function

-

Take the [stack] and [uncons] the top two items.

-

Example

-
   1 2 3 stununcons
-----------------------
-    1 2 3 3 2 [1]
-
-

Definition

-
-

[stack] [uncons] [uncons]

-
-

Crosslinks

-

[stuncons]

-
-

sub

-

Basis Function

-

Subtract the number on the top of the stack from the number -below it.

-
   a b sub
--------------
-    (a-b)
-
-

Crosslinks

-

[add]

-
-

succ

-

Function

-

Successor. Increment TOS.

-

Definition

-
-

1 +

-
-

Crosslinks

-

[pred]

-
-

sum

-

Combinator

-

Given a quoted sequence of numbers return the sum.

-

Example

-
   [1 2 3 4 5] sum
----------------------
-         15
-
-

Definition

-
-

[+] [step_zero]

-
-

Crosslinks

-

[size]

-
-

swaack

-

Basis Function

-

Swap stack. Take a list from the top of the stack, replace the -stack with the list, and put the old stack onto it.

-

Example

-
   1 2 3 [4 5 6] swaack
---------------------------
-   6 5 4 [3 2 1]
-
-

Discussion

-

This function works as a kind of "context switch". It's used in -the definition of [infra].

-

Crosslinks

-

[infra]

-
-

swap

-

Basis Function

-

Swap the top two items on the stack.

-
   a b swap
---------------
-     b a
-
-

Crosslinks

-

[swapd]

-
-

swapd

-

Function

-

Swap the second and third items on the stack.

-
   a b c swapd
------------------
-      b a c
-
-

Definition

-
-

[[swap]] [dip]

-
-

Crosslinks

-

[over] [tuck]

-
-

swoncat

-

Function

-

[concat] two lists, but [swap] the lists first.

-

Definition

-
-

[swap] [concat]

-
-

Crosslinks

-

[concat]

-
-

swons

-

Function

-

Like [cons] but [swap] the item and list.

-
   [...] a swons
--------------------
-      [a ...]
-
-

Definition

-
-

[swap] [cons]

-
-
-

tailrec

-

Combinator

-

A specialization of the [genrec] combinator.

-

Definition

-
-

[[i]] [genrec]

-
-

Discussion

-

Some recursive functions do not need to store additional data or -pending actions per-call. These are called "tail recursive" -functions. In Joy, they appear as [genrec] definitions that -have [i] for the second half of their recursive branch.

-

See the Recursion -Combinators notebook.

-

Crosslinks

-

[genrec]

-
-

take

-

Function

-

Expects an integer n and a list on the stack and -replace them with a list with just the top n items in -reverse order.

-
   [a b c d] 2 take
-----------------------
-        [b a]
-
-

Definition

-
-

[\<\<{}] [[shift]] [times] [pop]

-
-
-

ternary

-

Combinator

-

Run a quoted program using exactly three stack values and leave -the first item of the result on the stack.

-
   ... z y x [P] ternary
--------------------------
-         ... a
-
-

Definition

-
-

[binary] [popd]

-
-

Discussion

-

Runs any other quoted function and returns its first result -while consuming exactly three items from the stack.

-

Crosslinks

-

binary nullary -unary

-
-

third

-

Function

-
   [a b c ...] third
------------------------
-           c
-
-

Definition

-
-

[rest] [second]

-
-

Crosslinks

-

[first] [second] [fourth] [rest]

-
-

times

-

Combinator

-

Expect a quoted program and an integer n on the -stack and do the program n times.

-
   ... n [Q] . times
------------------------  w/ n <= 0
-         ... .
-
-   ... 1 [Q] . times
------------------------
-         ... . Q
-
-   ... n [Q] . times
--------------------------------------  w/ n > 1
-         ... . Q (n-1) [Q] times
-
-

Definition

-
-

[-- dip] cons [swap] infra [0 >] swap while pop :

-
-

Discussion

-

This works by building a little [while] program and running -it:

-
                 1 3 [++] • [-- dip] cons [swap] infra [0 >] swap while pop                                                                                                                 
-        1 3 [++] [-- dip] • cons [swap] infra [0 >] swap while pop                                                                                                                          
-        1 3 [[++] -- dip] • [swap] infra [0 >] swap while pop                                                                                                                               
- 1 3 [[++] -- dip] [swap] • infra [0 >] swap while pop                                                                                                                                      
-              dip -- [++] • swap [3 1] swaack [0 >] swap while pop                                                                                                                          
-              dip [++] -- • [3 1] swaack [0 >] swap while pop                                                                                                                               
-        dip [++] -- [3 1] • swaack [0 >] swap while pop                                                                                                                                     
-        1 3 [-- [++] dip] • [0 >] swap while pop                                                                                                                                            
-  1 3 [-- [++] dip] [0 >] • swap while pop                                                                                                                                                  
-  1 3 [0 >] [-- [++] dip] • while pop
-
-

This is a common pattern in Joy. You accept some parameters from -the stack which typically include qouted programs and use them to -build another program which does the actual work. This is kind of -like macros in Lisp, or preprocessor directives in C.

-
-

truthy

-

See bool.

-
-

tuck

-

Function

-

[dup] the item on the top of the stack under the second item on -the stack.

-
   a b tuck
---------------
-    b a b
-
-

Definition

-
-

[dup] [[swap]] [dip]

-
-

Crosslinks

-

[over]

-
-

unary

-

(Combinator)

-

Run a quoted program using exactly one stack value and leave the -first item of the result on the stack.

-
   ... x [P] unary
----------------------
-       ... a
-
-

Definition

-
-

[nullary] [popd]

-
-

Discussion

-

Runs any other quoted function and returns its first result -while consuming exactly one item from the stack.

-

Crosslinks

-

binary nullary -ternary

-
-

uncons

-

Basis Function

-

Removes an item from a list and leaves it on the stack under the -rest of the list. You cannot uncons an item from an -empty list.

-
   [a ...] uncons
---------------------
-      a [...]
-
-

Discussion

-

This is the inverse of [cons].

-

Crosslinks

-

[cons]

-
-

unique

-

Function

-

Given a list remove duplicate items.

-
-

unit

-

Function

-
   a unit
-------------
-    [a]
-
-

Definition

-
-

[] [cons]

-
-
-

unquoted

-

Combinator

-

Unquote (using [i]) the list that is second on the stack.

-

Example

-
   1 2 [3 4] 5 unquoted
---------------------------
-         1 2 3 4 5
-
-

Definition

-
-

[[i]] [dip]

-
-

Crosslinks

-

[unit]

-
-

unswons

-

Function

-
   [a ...] unswons
----------------------
-       [...] a
-
-

Definition

-
-

[uncons] [swap]

-
-
-

void

-

Basis Function

-

True if the form on TOS is void otherwise False.

-

Discussion

-

A form is any Joy expression composed solely of lists. This -represents a binary Boolean logical formula in the arithmetic of -the "Laws of Form", see The -Markable Mark

-
-

warranty

-

Basis Function

-

Print warranty information.

-
-

while

-

Combinator

-

A specialization of [loop] that accepts a quoted predicate -program P and runs it [nullary].

-
   [P] [F] while
-------------------- P -> false
-
-    [P] [F] while
---------------------- P -> true
-   F [P] [F] while
-
-

Definition

-
-

[swap] [nulco] [dupdipd] [concat] [loop]

-
-

Crosslinks

-

[loop]

-
-

words

-

Basis Function

-

Print all the words in alphabetical order.

-

Discussion

-

Mathematically this is a form of [id].

-

Crosslinks

-

[help]

-
-

x

-

Combinator

-

Take a quoted function F and run it with itself as -the first item on the stack.

-
   [F] x
------------
-   [F] F
-
-

Definition

-
dup i
-
-

Discussion

-

The simplest recursive pattern.

-

See the Recursion -Combinators notebook. as well as Recursion -Theory and Joy by Manfred von

-
-

xor

-

Basis Function

-

Logical bit-wise eXclusive OR.

-

Crosslinks

-

[and] [or]

-
-

zip

-

Function

-

Replace the two lists on the top of the stack with a list of the -pairs from each list. The smallest list sets the length of the -result list.

-

Example

-
   [1 2 3] [4 5 6] zip
--------------------------
-   [[4 1] [5 2] [6 3]]
-
- - diff --git a/docs/html/FuncRef.html b/docs/html/FuncRef.html new file mode 100644 index 0000000..9d7ed40 --- /dev/null +++ b/docs/html/FuncRef.html @@ -0,0 +1,2501 @@ + + + + + + + Function Reference + + + + +
+

Function Reference

+
+ +

Version -10.0.0

+

Each function, combinator, or definition should be documented here.

+
+

&

+

See and.

+
+

&&

+

Combinator

+

Short-circuiting Boolean AND

+

Accept two quoted programs, run the first and expect a Boolean value, if it’s true pop it and run the second program (which should also return a Boolean value) otherwise pop the second program (leaving false on the stack.)

+
   [A] [B] &&
+---------------- true
+        B
+
+
+   [A] [B] &&
+---------------- false
+     false
+

Definition

+
nulco [nullary [false]] dip branch
+

Derivation

+

TODO: this is derived in one of the notebooks I think, look it up and link to it, or copy the content here.

+

Discussion

+

This is seldom useful, I suspect, but this way you have it.

+ +

||

+
+

*

+

See mul.

+
+

•

+

See id.

+
+

^

+

See xor.

+
+

=

+

See eq.

+
+

!=

+

See ne.

+
+

!-

+

Function

+

Not negative.

+
    n !-
+----------- n < 0
+   false
+
+
+   n !-
+---------- n >= 0
+   true
+

Definition

+
0 \>=
+

Discussion

+

Return a Boolean value indicating if a number is greater than or equal to zero.

+
+

>

+

See gt.

+
+

>=

+

See ge.

+
+

>>

+

See rshift.

+
+

-

+

See sub.

+
+

–

+

See pred.

+
+

<

+

See lt.

+
+

<=

+

See le.

+
+

<>

+

See ne.

+
+

<{}

+

Function

+
   ... a <{}
+----------------
+   ... [] a
+

Definition

+
[] swap
+

Discussion

+

Tuck an empty list just under the first item on the stack.

+ +

<<{}

+
+

<<

+

See lshift.

+
+

<<{}

+

Function

+
   ... b a <{}
+-----------------
+   ... [] b a
+

Definition

+
[] rollup
+

Discussion

+

Tuck an empty list just under the first two items on the stack.

+ +

<{}

+
+

%

+

See mod.

+
+

+

+

See add.

+
+

++

+

See succ.

+
+

?

+

Function

+

Is the item on the top of the stack “truthy”?

+

Definition

+
+

dup bool

+
+

Discussion

+

You often want to test the truth value of an item on the stack without consuming the item.

+ +

bool

+
+

/

+

See floordiv.

+
+

//

+

See floordiv.

+
+

/floor

+

See floordiv.

+
+

||

+

Combinator

+

Short-circuiting Boolean OR

+

Definition

+
+

nulco [nullary] dip [true] branch

+
+

Discussion

+

Accept two quoted programs, run the first and expect a Boolean value, if it’s false pop it and run the second program (which should also return a Boolean value) otherwise pop the second program (leaving true on the stack.)

+
   [A] [B] ||
+---------------- A -> false
+        B
+
+
+   [A] [B] ||
+---------------- A -> true
+      true
+ +

&&

+
+

abs

+

Function

+

Return the absolute value of the argument.

+

Definition

+
+

dup 0 < [] [neg] branch

+
+
+

add

+

Basis Function

+

Add two numbers together: a + b.

+
+

anamorphism

+

Combinator

+

Build a list of values from a generator program G and a stopping predicate P.

+
           [P] [G] anamorphism
+-----------------------------------------
+   [P] [pop []] [G] [dip swons] genrec
+

Definition

+
+

[pop []] swap [dip swons] genrec

+
+

Example

+

The range function generates a list of the integers from 0 to n - 1:

+
+

[0 <=] [-- dup] anamorphism

+
+

Discussion

+

See the Recursion Combinators notebook.

+
+

and

+

Basis Function

+

Logical bit-wise AND.

+ +

or xor

+
+

app1

+

“apply one”

+

Combinator

+

Given a quoted program on TOS and anything as the second stack item run the program without disturbing the stack and replace the two args with the first result of the program.

+
         ... x [Q] app1
+---------------------------------
+   ... [x ...] [Q] infra first
+

This is the same effect as the unary combinator.

+

Definition

+
+

nullary popd

+
+

Discussion

+

Just a specialization of nullary really. Its parallelizable cousins are more useful.

+ +

app2 app3 appN unary

+
+

app2

+

Combinator

+

Like app1 with two items.

+
   ... y x [Q] . app2
+-----------------------------------
+   ... [y ...] [Q] . infra first
+       [x ...] [Q]   infra first
+

Definition

+
+

[grba swap grba swap] dip [infrst] cons ii

+
+

Discussion

+

Unlike app1, which is essentially an alias for unary, this function is not the same as binary. Instead of running one program using exactly two items from the stack and pushing one result (as binary does) this function takes two items from the stack and runs the program twice, separately for each of the items, then puts both results onto the stack.

+

This is not currently implemented as parallel processes but it can (and should) be done.

+ +

app1 app3 appN unary

+
+

app3

+

Combinator

+

Like app1 with three items.

+
     ... z y x [Q] . app3
+-----------------------------------
+   ... [z ...] [Q] . infra first
+       [y ...] [Q]   infra first
+       [x ...] [Q]   infra first
+

Definition

+
+

3 appN

+
+

Discussion

+

See app2.

+ +

app1 app2 appN unary

+
+

appN

+

Combinator

+

Like app1 with any number of items.

+
   ... xN ... x2 x1 x0 [Q] n . appN
+--------------------------------------
+   ... [xN ...] [Q] . infra first
+                   ...
+       [x2 ...] [Q]   infra first
+       [x1 ...] [Q]   infra first
+       [x0 ...] [Q]   infra first
+

Definition

+
+

[grabN] codi map disenstacken

+
+

Discussion

+

This function takes a quoted function Q and an integer and runs the function that many times on that many stack items. See also app2.

+ +

app1 app2 app3 unary

+
+

at

+

See getitem.

+
+

average

+

Function

+

Compute the average of a list of numbers. (Currently broken until I can figure out what to do about “numeric tower” in Thun.)

+

Definition

+
+

[sum] [size] cleave /

+
+

Discussion

+

Theoretically this function would compute the sum and the size in two separate threads, then divide. This works but a compiled version would probably do better to sum and count the list once, in one thread, eh?

+

As an exercise in Functional Programming in Joy it would be fun to convert this into a catamorphism. See the Recursion Combinators notebook.

+
+

b

+

Combinator

+

Run two quoted programs

+
   [P] [Q] b
+---------------
+      P Q
+

Definition

+
+

[i] dip i

+
+

Discussion

+

This combinator may seem trivial but it comes in handy.

+ +

dupdip ii

+
+

binary

+

Combinator

+

Run a quoted program using exactly two stack values and leave the first item of the result on the stack.

+
   ... y x [P] binary
+-----------------------
+        ... a
+

Definition

+
+

unary popd

+
+

Discussion

+

Runs any other quoted function and returns its first result while consuming exactly two items from the stack.

+ +

nullary ternary unary

+
+

bool

+

Basis Function

+

Convert the item on the top of the stack to a Boolean value.

+

Discussion

+

For integers 0 is false and any other number is true; for lists the empty list is false and all other lists are true.

+ +

not

+
+

branch

+

Basis Combinator

+

Use a Boolean value to select and run one of two quoted programs.

+
   false [F] [T] branch
+--------------------------
+          F
+
+   true [F] [T] branch
+-------------------------
+             T
+

Definition

+
+

rolldown choice i

+
+

Discussion

+

This is one of the fundamental operations (although it can be defined in terms of choice as above). The more common “if..then..else” construct ifte adds a predicate function that is evaluated nullary.

+ +

choice ifte select

+
+

ccccons

+

Function

+
   a b c d [...] ccccons
+---------------------------
+       [a b c d ...]
+

Do cons four times.

+

Definition

+
+

ccons ccons

+
+ +

ccons cons times

+
+

ccons

+

Function

+
   a b [...] ccons
+---------------------
+      [a b ...]
+

Do cons two times.

+

Definition

+
+

cons cons

+
+ +

cons ccons

+
+

choice

+

Basis Function

+

Use a Boolean value to select one of two items.

+
   a b false choice
+----------------------
+          a
+
+   a b true choice
+---------------------
+          b
+

Definition

+
+

[pop] [popd] branch

+
+

Discussion

+

It’s a matter of taste whether you implement this in terms of branch or the other way around.

+ +

branch select

+
+

clear

+

Basis Function

+

Clear everything from the stack.

+

Definition

+
+

stack bool [pop stack bool] loop

+
+ +

stack swaack

+
+

cleave

+

Combinator

+

Run two programs in parallel, consuming one additional item, and put their results on the stack.

+
   ... x [A] [B] cleave
+------------------------
+        ... a b
+

Derivation

+
+

fork popdd

+
+

Example

+
   1 2 3 [+] [-] cleave
+--------------------------
+         1 2 5 -1
+

Discussion

+

One of a handful of useful parallel combinators.

+ +

clop fork map

+
+

clop

+

Combinator

+

Run two programs in parallel, consuming two additional items, and put their results on the stack.

+
   ... x y [A] [B] clop
+--------------------------
+        ... a b
+

Definition

+
+

cleave popdd

+
+

Discussion

+

Like cleave but consumes an additional item from the stack.

+
   1 2 3 4 [+] [-] clop
+--------------------------
+         1 2 7 -1
+ +

cleave fork map

+
+

cmp

+

Combinator

+

Take two values and three quoted programs on the stack and run one of the three depending on the results of comparing the two values.

+
   a b [G] [E] [L] cmp
+------------------------- a > b
+        G
+
+   a b [G] [E] [L] cmp
+------------------------- a = b
+            E
+
+   a b [G] [E] [L] cmp
+------------------------- a < b
+                L
+

Discussion

+

This is useful sometimes, and you can dup or dupd with two quoted programs to handle the cases when you just want to deal with <= or >= and not all three possibilities, e.g.:

+
[G] [EL] dup cmp
+
+[GE] [L] dupd cmp
+

Or even:

+
[GL] [E] over cmp
+ +

TODO: link to tree notebooks where this was used.

+
+

codi

+

Combinator

+

Take a quoted program from the stack, cons the next item onto it, then dip the whole thing under what was the third item on the stack.

+
   a b [F] . codi
+--------------------
+         b . F a
+

Definition

+
+

cons dip

+
+

Discussion

+

This is one of those weirdly specific functions that turns out to be useful in a few places.

+ +

appN codireco

+
+

codireco

+

Combinator

+

This is part of the make_generator function. You would not use this combinator directly.

+

Definition

+
+

codi reco

+
+

Discussion

+

See make_generator and the “Using x to Generate Values” notebook as well as Recursion Theory and Joy by Manfred von Thun.

+ +

make_generator

+
+

concat

+

Function

+

Concatinate two lists.

+
   [a b c] [d e f] concat
+----------------------------
+       [a b c d e f]
+ +

first first_two flatten fourth getitem remove rest reverse rrest second shift shunt size sort split_at split_list swaack third zip

+
+

cond

+

Combinator

+

This combinator works like a case statement. It expects a single quote on the stack that must contain zero or more condition quotes and a default quote. Each condition quote should contain a quoted predicate followed by the function expression to run if that predicate returns true. If no predicates return true the default function runs.

+
[
+    [ [Predicate0] Function0 ]
+    [ [Predicate1] Function1 ]
+    ...
+    [ [PredicateN] FunctionN ]
+    [Default]
+]
+cond
+

Discussion

+

It works by rewriting into a chain of nested ifte expressions, e.g.:

+
      [[[B0] T0] [[B1] T1] [D]] cond
+-----------------------------------------
+   [B0] [T0] [[B1] [T1] [D] ifte] ifte
+ +

ifte

+
+

cons

+

Basis Function

+

Given an item and a list, append the item to the list to make a new list.

+
   a [...] cons
+------------------
+     [a ...]
+

Discussion

+

Cons is a venerable old function from Lisp. Its inverse operation is uncons.

+ +

uncons

+
+

dinfrirst

+

Combinator

+

Specialist function (that means I forgot what it does and why.)

+

Definition

+
+

dip infrst

+
+
+

dip

+

Basis Combinator

+

The dip combinator expects a quoted program on the stack and below it some item, it hoists the item into the expression and runs the program on the rest of the stack.

+
   ... x [Q] . dip
+---------------------
+         ... . Q x
+

Discussion

+

This along with infra are enough to update any datastructure. See the “Traversing Datastructures with Zippers” notebook.

+

Note that the item that was on the top of the stack (x in the example above) will not be treated specially by the interpreter when it is reached again. This is something of a footgun. My advice is to avoid putting bare unquoted symbols onto the stack, but then you can’t use symbols as “atoms” and also use dip and infra to operate on compound datastructures with atoms in them. This is a kind of side-effect of the Continuation-Passing Style. The dip combinator could “set aside” the item and replace it after running Q but that means that there is an “extra space” where the item resides while Q runs. One of the nice things about CPS is that the whole state is recorded in the stack and pending expression (not counting modifications to the dictionary.)

+ +

dipd dipdd dupdip dupdipd infra

+
+

dipd

+

Combinator

+

Like dip but expects two items.

+
   ... y x [Q] . dipd
+-------------------------
+           ... . Q y x
+

Discussion

+

See dip.

+ +

dip dipdd dupdip dupdipd infra

+
+

dipdd

+

Combinator

+

Like dip but expects three items. :

+
   ... z y x [Q] . dip
+-----------------------------
+             ... . Q z y x
+

Discussion

+

See dip.

+ +

dip dipd dupdip dupdipd infra

+
+

disenstacken

+

Function

+

The disenstacken function expects a list on top of the stack and makes that the stack discarding the rest of the stack.

+
   1 2 3 [4 5 6] disenstacken
+--------------------------------
+            6 5 4
+

Definition

+
+

[clear] dip reverse unstack

+
+

Discussion

+

Note that the order of the list is not changed, it just looks that way because the stack is printed with the top on the right while lists are printed with the top or head on the left.

+ +

enstacken stack unstack

+
+

div

+

See floordiv.

+
+

divmod

+

Function

+
    x y divmod
+------------------
+     q      r
+   (x/y)  (x%y)
+

Invariant: qy + r = x.

+

Definition

+
+

[floordiv] [mod] clop

+
+
+

down_to_zero

+

Function

+

Given a number greater than zero put all the Natural numbers (including zero) less than that onto the stack.

+

Example

+
   3 down_to_zero
+--------------------
+      3 2 1 0
+

Definition

+
+

[0 >] [dup –] while

+
+ +

range

+
+

drop

+

Function

+

Expects an integer and a quote on the stack and returns the quote with n items removed off the top.

+

Example

+
   [a b c d] 2 drop
+----------------------
+       [c d]
+

Definition

+
+

[rest] times

+
+ +

take

+
+

dup

+

Basis Function

+

“Dup”licate the top item on the stack.

+
   a dup
+-----------
+    a a
+ +

dupd dupdd dupdip dupdipd

+
+

dupd

+

Function

+

dup the second item down on the stack.

+
   a b dupd
+--------------
+    a a b
+

Definition

+
+

[dup] dip

+
+ +

dup dupdd dupdip dupdipd

+
+

dupdd

+

Function

+

dup the third item down on the stack.

+
   a b c dupdd
+-----------------
+     a a b c
+

Definition

+
+

[dup] dipd

+
+ +

dup dupd dupdip dupdipd

+
+

dupdip

+

Combinator

+

Apply a function F and dup the item under it on the stack.

+
   a [F] dupdip
+------------------
+      a F a
+

Definition

+
+

dupd dip

+
+

Derivation

+
a [F] dupdip
+a [F] dupd dip
+a [F] [dup] dip dip
+a dup [F] dip
+a a [F] dip
+a F a
+

Discussion

+

A very common and useful combinator.

+ +

dupdipd

+
+

dupdipd

+

Combinator

+

Run a copy of program F under the next item down on the stack.

+
   a [F] dupdipd
+-------------------
+      F a [F]
+

Definition

+
+

dup dipd

+
+ +

dupdip

+
+

enstacken

+

Function

+

Put the stack onto the stack replacing the contents of the stack.

+
   ... a b c enstacken
+-------------------------
+       [c b a ...]
+

Definition

+
+

stack [clear] dip

+
+

Discussion

+

This is a destructive version of stack. See the note under disenstacken about the apparent but illusory reversal of the stack.

+ +

stack [unstack] disenstacken

+
+

eq

+

Basis Function

+

Compare the two items on the top of the stack for equality and replace them with a Boolean value.

+
   a b eq
+-------------
+   Boolean
+   (a = b)
+ +

cmp ge gt le lt ne

+
+

first

+

Function

+

Replace a list with its first item.

+
   [a ...]
+--------------
+      a
+

Definition

+
+

uncons pop

+
+ +

second third fourth rest

+
+

first_two

+

Function

+

Replace a list with its first two items.

+
   [a b ...] first_two
+-------------------------
+           a b
+

Definition

+
+

uncons first

+
+ +

first second third fourth rest

+
+

flatten

+

Function

+

Given a list of lists, concatinate them.

+

Example

+
   [[1 2] [3 [4] 5] [6 7]] flatten
+-------------------------------------
+          [1 2 3 [4] 5 6 7]
+

Definition

+
+

<{} [concat] step

+
+

Discussion

+

Note that only one “level” of lists is flattened. In the example above [4] is not unquoted.

+ +

concat first first_two fourth getitem remove rest reverse rrest second shift shunt size sort split_at split_list swaack third zip

+
+

floor

+

Basis Function

+

Return the largest integer <= x.

+

Discussion

+

This function doesn’t make sense (yet) to have because there are (as yet) only integers in the system.

+
+

floordiv

+

Basis Function

+

I don’t know why this is called “floor” div, I think it rounds its result down (not towards zero or up.)

+
   a b floordiv
+------------------
+      (a/b)
+

Discussion

+

All the division commands need to be revisited when the “numeric tower” for Thun gets nailed down.

+ +

divmod

+
+

fork

+

Combinator

+

Run two quoted programs in parallel and replace them with their results.

+
   ... [F] [G] fork
+----------------------
+       ... f g
+

Definition

+
+

[i] app2

+
+

Discussion

+

The basic parallelism combinator, the two programs are run independently.

+ +

cleave clop map

+
+

fourth

+

Function

+

Replace a list with its fourth item.

+
   [a b c d ...] fourth
+--------------------------
+          d
+

Definition

+
+

rest third

+
+ +

first second third rest

+
+

gcd

+

Function

+

Take two integers from the stack and replace them with their Greatest Common Denominator.

+

Definition

+
+

true [tuck mod dup 0 >] loop pop

+
+

Discussion

+

Euclid’s Algorithm

+
+

gcd2

+

Function

+

Compiled GCD function.

+

Discussion

+

See gcd.

+ +

gcd

+
+

ge

+

Basis Function

+

Greater-than-or-equal-to comparison of two numbers.

+
   a b ge
+--------------
+   Boolean
+   (a >= b)
+ +

cmp eq gt le lt ne

+
+

genrec

+

Combinator

+

General Recursion Combinator.

+
                      [if] [then] [rec1] [rec2] genrec
+---------------------------------------------------------------------
+   [if] [then] [rec1 [[if] [then] [rec1] [rec2] genrec] rec2] ifte
+

Definition

+
+

[[genrec] ccccons] nullary swons concat ifte

+
+

(Note that this definition includes the genrec symbol itself, it is self-referential. This is possible because the definition machinery does not check that symbols in defs are in the dictionary. genrec is the only self-referential definition.)

+

Discussion

+

See the Recursion Combinators notebook.

+

From “Recursion Theory and Joy” by Manfred von Thun:

+
+

“The genrec combinator takes four program parameters in addition to whatever data parameters it needs. Fourth from the top is an if-part, followed by a then-part. If the if-part yields true, then the then-part is executed and the combinator terminates. The other two parameters are the rec1-part and the rec2-part. If the if-part yields false, the rec1-part is executed. Following that the four program parameters and the combinator are again pushed onto the stack bundled up in a quoted form. Then the rec2-part is executed, where it will find the bundled form. Typically it will then execute the bundled form, either with i or with app2, or some other combinator.”

+
+

The way to design one of these is to fix your base case [then] and the test [if], and then treat rec1 and rec2 as an else-part “sandwiching” a quotation of the whole function.

+

For example, given a (general recursive) function F:

+
F == [I] [T] [R1] [R2] genrec
+

If the [I] if-part fails you must derive R1 and R2 from: :

+
... R1 [F] R2
+

Just set the stack arguments in front, and figure out what R1 and R2 have to do to apply the quoted [F] in the proper way. In effect, the genrec combinator turns into an ifte combinator with a quoted copy of the original definition in the else-part:

+
F == [I] [T] [R1]   [R2] genrec
+  == [I] [T] [R1 [F] R2] ifte
+

Tail recursive functions are those where R2 is the i combinator:

+
P == [I] [T] [R] tailrec
+  == [I] [T] [R [P] i] ifte
+  == [I] [T] [R P] ifte
+ +

anamorphism tailrec x

+
+

getitem

+

Function

+

Expects an integer and a quote on the stack and returns the item at the nth position in the quote counting from 0.

+

Example

+
   [a b c d] 2 getitem
+-------------------------
+        c
+

Definition

+
+

drop first

+
+

Discussion

+

If the number isn’t a valid index into the quote getitem will cause some sort of problem (the exact nature of which is implementation-dependant.)

+ +

concat first first_two flatten fourth remove rest reverse rrest second shift shunt size sort split_at split_list swaack third zip

+
+

grabN

+

Function

+

Expect a number on the top of the stack and cons that many items from under it onto a new list.

+

Example

+
   a b c d e 3 grabN
+-----------------------
+      a b [c d e]
+

Definition

+
+

<{} [cons] times

+
+
+

grba

+

Function

+

A weird function used in app2 that does this:

+
      ... 1 2 3 4 5 grba
+-------------------------------
+   ... 1 2 3 [4 3 2 1 ...] 5
+

It grabs the stack under the top item, and substitutes it for the second item down on the stack.

+

Definition

+
+

[stack popd] dip

+
+

Discussion

+

This function “grabs” an item from the stack along with a copy of the stack. It’s part of the app2 definition.

+ +

app2

+
+

gt

+

Basis Function

+

Greater-than comparison of two numbers.

+
   a b gt
+--------------
+   Boolean
+   (a > b)
+ +

cmp eq ge le lt ne

+
+

help

+

Function

+

Accepts a quoted symbol on the top of the stack and prints its documentation.

+
   [foo] help
+----------------
+

Discussion

+

Technically this is equivalent to pop, but it will only work if the item on the top of the stack is a quoted symbol.

+
+

hypot

+

Function

+
         x y hypot
+---------------------------
+   sqrt(sqr(x) + sqr(y))
+

Definition

+
+

[sqr] ii + sqrt

+
+

Discussion

+

This is another function that has to wait on the numeric tower.

+ +

sqrt

+
+

i

+

Basis Combinator

+

Append a quoted expression onto the pending expression.

+
   [Q] . i
+-------------
+       . Q
+

Discussion

+

This is a fundamental combinator. It is used in all kinds of places. For example, the x combinator can be defined as dup i.

+
+

id

+

Basis Function

+

The identity function.

+

Discussion

+

Does nothing. It’s kind of a mathematical thing, but it occasionally comes in handy.

+
+

ifte

+

Combinator

+

If-Then-Else combinator, a common and convenient specialization of branch.

+
        [if] [then] [else] ifte
+---------------------------------------
+   [if] nullary [else] [then] branch
+

Definition

+
+

[nullary] dipd swap branch

+
+ +

branch loop while

+
+

ii

+

Combinator

+

Take a quoted program from the stack and run it twice, first under the top item, then again with the top item.

+
... a [Q] ii
+------------------
+ ... Q a Q
+

Definition

+
+

[dip] dupdip i

+
+

Example

+

It’s a little tricky to understand how this works so here’s an example trace:

+
      1 2 3 4 [++] • [dip] dupdip i
+1 2 3 4 [++] [dip] • dupdip i
+      1 2 3 4 [++] • dip [++] i
+             1 2 3 • ++ 4 [++] i
+             1 2 4 • 4 [++] i
+           1 2 4 4 • [++] i
+      1 2 4 4 [++] • i
+           1 2 4 4 • ++
+           1 2 4 5 •
+

Discussion

+

In some cases (like the example above) this is the same effect as using app2 but most of the time it’s not:

+
   1 2 3 4 [+] ii
+--------------------
+        1 9
+
+   1 2 3 4 [+] app2
+----------------------
+       1 2 5 6
+ +

app2 b

+
+

infra

+

Combinator

+

Accept a quoted program and a list on the stack and run the program with the list as its stack. Does not affect the stack (below the list.)

+
   ... x y z [a b c] [Q] infra
+---------------------------------
+    c b a Q [z y x ...] swaack
+

Definition

+
+

swons swaack [i] dip swaack

+
+

Discussion

+

This is one of the more useful combinators. It allows a quoted expression to serve as a stack for a program, effectively running it in a kind of “pocket universe”. If the list represents a datastructure then infra lets you work on its internal structure.

+ +

swaack

+
+

infrst

+

Combinator

+

Does infra and then extracts the first item from the resulting list.

+

Definition

+
+

infra first

+
+
+

inscribe

+

Create a new Joy function definition in the Joy dictionary. A definition is given as a quote with a name followed by a Joy expression.

+

Example

+
[sqr dup mul] inscribe
+

Discussion

+

This is the only function that modifies the dictionary. It’s provided as a convenience, for tinkering with new definitions before entering them into the defs.txt file. It can be abused, which you should avoid unless you know what you’re doing.

+
+

le

+

Basis Function

+

Less-Than-or-Equal-to comparison of the two items on the top of the stack, replacing them with a Boolean value.

+
   a b le
+-------------
+   Boolean
+   (a <= b)
+ +

cmp eq ge gt lt ne

+
+

loop

+

Basis Combinator

+

Expect a quoted program Q and a Boolean value on the stack. If the value is false discard the quoted program, otherwise run a copy of Q and loop again.

+
   false [Q] loop
+--------------------
+
+
+   true [Q] . loop
+--------------------------
+            . Q [Q] loop
+

Discussion

+

This, along with branch and fork, is one of the four main combinators of all programming. The fourth, sequence, is implied by juxtaposition. That is to say, in Joy F G is like G(F(...)) in a language bassed on function application. Or again, to quote the Joy Wikipedia entry,

+
+

In Joy, the meaning function is a homomorphism from the syntactic monoid onto the semantic monoid. That is, the syntactic relation of concatenation of symbols maps directly onto the semantic relation of composition of functions.

+
+

Anyway, branch, fork, amd loop are the fundamental combinators in Joy. Just as branch has it’s more common and convenient form ifte, loop has while.

+ +

branch fork while

+
+

lshift

+

Basis Function

+

Logical Left-Shift

+
   a n lshift
+----------------
+     (a×2ⁿ)
+ +

rshift

+
+

lt

+

Basis Function

+

Less-Than comparison of the two items on the top of the stack, replacing them with a Boolean value.

+
   a b lt
+-------------
+   Boolean
+   (a < b)
+ +

cmp eq ge gt le ne

+
+

make_generator

+

Function

+

Given an initial state value and a quoted generator function build a generator quote.

+
   state [generator function] make_generator
+-----------------------------------------------
+     [state [generator function] codireco]
+

Example

+
   230 [dup ++] make_generator
+---------------------------------
+     [230 [dup ++] codireco]
+

And then:

+
   [230 [dup ++] codireco] 5 [x] times pop
+---------------------------------------------
+             230 231 232 233 234
+

Definition

+
+

[codireco] ccons

+
+

Discussion

+

See the “Using x to Generate Values” notebook.

+ +

codireco

+
+

map

+

Combinator

+

Given a list of items and a quoted program run the program for each item in the list (with the rest of the stack) and replace the old list and the program with a list of the results.

+

Example

+
   5 [1 2 3] [++ *] map
+--------------------------
+       5 [10 15 20]
+

Discussion

+

This is a common operation in many languages. In Joy it can be a parallelism combinator due to the “pure” nature of the language.

+ +

app1 app2 app3 appN fork

+
+

max

+

Basis Function

+

Given a list find the maximum.

+

Example

+
   [1 2 3 4] max
+-------------------
+         4
+ +

min size sum

+
+

min

+

Basis Function

+

Given a list find the minimum.

+

Example

+
   [1 2 3 4] min
+-------------------
+         1
+ +

max size sum

+
+

mod

+

Basis Function

+

Return the remainder of a divided by b.

+
   a b mod
+-------------
+    (a%b)
+ +

divmod mul

+
+

modulus

+

See mod.

+
+

mul

+

Basis Function

+

Multiply two numbers.

+
   a b mul
+-------------
+    (a×b)
+ +

div product

+
+

ne

+

Basis Function

+

Not-Equal comparison of the two items on the top of the stack, replacing them with a Boolean value.

+
   a b ne
+-------------
+   Boolean
+   (a = b)
+ +

cmp eq ge gt le lt

+
+

neg

+

Function

+

Invert the sign of a number.

+
   a neg
+-----------
+    -a
+

Definition

+
+

0 swap -

+
+
+

not

+

Function

+

Like bool but convert the item on the top of the stack to the inverse Boolean value.

+
   true not
+--------------
+    false
+
+   false not
+---------------
+     true
+

Definition

+
+

bool [true] [false] branch

+
+ +

bool

+
+

nulco

+

Function

+

Take the item on the top of the stack and cons it onto [nullary].

+
     [F] nulco
+-------------------
+   [[F] nullary]
+

Definition

+
+

[nullary] cons

+
+

Discussion

+

Helper function for || and &&.

+ +

&& ||

+
+

nullary

+

Combinator

+

Run a quoted program without using any stack values and leave the first item of the result on the stack.

+
   ... [P] nullary
+---------------------
+        ... a
+

Definition

+
+

[stack] dip infra first

+
+

Example

+
... [P] nullary
+... [P] [stack] dip infra first
+... stack [P] infra first
+... [...] [P] infra first
+... [a ...] first
+...  a
+

Discussion

+

A very useful function that runs any other quoted function and returns it’s first result without disturbing the stack (under the quoted program.)

+ +

unary binary ternary

+
+

of

+

Function

+

Like getitem but swaps the order of arguments.

+

Example

+
   2 [a b c d] of
+--------------------
+         c
+

Definition

+
+

swap getitem

+
+ +

getitem

+
+

or

+

Basis Function

+

Logical bit-wise OR.

+ +

and xor

+
+

over

+

Function

+

dup the second item on the stack over the first.

+
   a b over
+--------------
+    a b a
+

Definition

+

There are many many ways to define this function.

+
+

swap tuck

+
+
+

[pop] nullary

+
+
+

[dup] dip swap

+
+
+

unit dupdip

+
+
+

unit dupdipd first

+
+

And so on…

+

Discussion

+

A fine old word from Forth.

+ +

tuck

+
+

pam

+

Combinator

+

Take a list of quoted functions from the stack and replace it with a list of the first results from running those functions (on copies of the rest of the stack.)

+

Example

+
   5 7 [[+][-][*][/][%]] pam
+-------------------------------
+      5 7 [12 -2 35 0 5]
+

Definition

+
+

[i] map

+
+

Discussion

+

A specialization of map that runs a list of functions in parallel (if the underlying map function is so implemented, of course.)

+ +

map

+
+

pick

+

See getitem.

+
+

pm

+

Function

+

Plus or minus. Replace two numbers with their sum and difference.

+
      a b pm
+-----------------
+   (a+b) (a-b)
+

Definition

+
+

[+] [-] clop

+
+
+

pop

+

Basis Function

+

Pop the top item from the stack and discard it.

+
   a pop
+-----------
+ +

popd popdd popop popopd popopdd popopop

+
+

popd

+

Function

+

pop the second item down on the stack.

+
   a b popd
+--------------
+      b
+

Definition

+
+

swap pop

+
+ +

pop popdd popop popopd popopdd popopop

+
+

popdd

+

Function

+

pop the third item on the stack.

+
   a b c popdd
+-----------------
+       b c
+

Definition

+
+

rolldown pop

+
+ +

pop popd popop popopd popopdd popopop

+
+

popop

+

Function

+

pop two items from the stack.

+
   a b popop
+---------------
+

Definition

+
+

pop pop

+
+ +

pop popd popdd popopd popopdd popopop

+
+

popopd

+

Function

+

pop the second and third items from the stack.

+
   a b c popopd
+------------------
+        c
+

Definition

+
+

rollup popop

+
+ +

pop popd popdd popop popopdd popopop

+
+

popopdd

+

Function

+
   a b c d popopdd
+---------------------
+        c d
+

Definition

+
+

[popop] dipd

+
+ +

pop popd popdd popop popopd popopop

+
+

popopop

+

Function

+

pop three items from the stack.

+
   a b c popopop
+-------------------
+

Definition

+
+

pop popop

+
+ +

pop popd popdd popop popopd popopdd

+
+

pow

+

Basis Function

+

Take two numbers a and b from the stack and raise a to the nth power. (b is on the top of the stack.)

+
   a n pow
+-------------
+    (aⁿ)
+

Example

+
   2 [2 3 4 5 6 7 8 9] [pow] map
+-----------------------------------
+    2 [4 8 16 32 64 128 256 512]
+
+

pred

+

Function

+

Predecessor. Decrement TOS.

+

Definition

+
+

1 -

+
+ +

succ

+
+

primrec

+

Combinator

+

From the “Overview of the language JOY”

+
+

The primrec combinator expects two quoted programs in addition to a data parameter. For an integer data parameter it works like this: If the data parameter is zero, then the first quotation has to produce the value to be returned. If the data parameter is positive then the second has to combine the data parameter with the result of applying the function to its predecessor.

+
+
+

5 [1] [*] primrec

+
+
+

Then primrec tests whether the top element on the stack (initially the 5) is equal to zero. If it is, it pops it off and executes one of the quotations, the [1] which leaves 1 on the stack as the result. Otherwise it pushes a decremented copy of the top element and recurses. On the way back from the recursion it uses the other quotation, [*], to multiply what is now a factorial on top of the stack by the second element on the stack.

+
+
   0 [Base] [Recur] primrec
+------------------------------
+      Base
+
+         n [Base] [Recur] primrec
+------------------------------------------ n > 0
+   n (n-1) [Base] [Recur] primrec Recur
+

Discussion

+

Simple and useful specialization of the genrec combinator from the original Joy system.

+ +

genrec tailrec

+
+

product

+

Function

+

Just as sum sums a list of numbers, this function multiplies them together.

+

Definition

+
+

1 swap [mul] step

+
+

Or,

+
+

[1] [mul] primrec

+
+
+

quoted

+

Function

+

“Quote D” Wrap the second item on the stack in a list.

+
   a b quoted
+----------------
+     [a] b
+

Definition

+
+

[unit] dip

+
+

Discussion

+

This comes from the original Joy stuff.

+ +

unit

+
+

range

+

Function

+

Expect a number n on the stack and replace it with a list: [(n-1)...0].

+

Example

+
     5 range
+-----------------
+   [4 3 2 1 0]
+
+   -5 range
+--------------
+      []
+

Definition

+
+

[0 <=] [1 - dup] anamorphism

+
+

Discussion

+

If n is less than 1 the resulting list is empty.

+ +

range_to_zero

+
+

range_to_zero

+

Function

+

Take a number n from the stack and replace it with a list [0...n].

+

Example

+
   5 range_to_zero
+---------------------
+    [0 1 2 3 4 5]
+

Definition

+
+

unit [down_to_zero] infra

+
+

Discussion

+

Note that the order is reversed compared to range.

+ +

down_to_zero range

+
+

reco

+

Function

+

Replace the first item in a list with the item under it.

+
   a [b ...] reco
+--------------------
+     [a ...]
+

Definition

+
+

rest cons

+
+ +

codireco make_generator

+
+

rem

+

See mod.

+
+

remainder

+

See mod.

+
+

remove

+

Function

+

Expects an item on the stack and a quote under it and removes that item from the the quote. The item is only removed once. If the list is empty or the item isn’t in the list then the list is unchanged.

+
   [1 2 3 1] 1 remove
+------------------------
+        [2 3 1]
+

Definition

+

See the “Remove Function” notebook.

+
+

rest

+

Basis Function

+
   [a ...] rest
+------------------
+      [...]
+ +

first uncons

+
+

reverse

+

Function

+

Reverse the list on the top of the stack.

+

Example

+
   [1 2 3] reverse
+---------------------
+       [3 2 1]
+

Definition

+
+

<{} shunt

+
+
+

rolldown

+

Function

+
   a b c rolldown
+--------------------
+       b c a
+

Definition

+
+

swapd swap

+
+ +

rollup

+
+

rollup

+

Function

+
   a b c rollup
+------------------
+      c a b
+

Definition

+
+

swap swapd

+
+ +

rolldown

+
+

roll>

+

See rollup.

+
+

roll<

+

See rolldown.

+
+

round

+

Function

+

Round a number to a given precision in decimal digits.

+

Discussion

+

Another one that won’t make sense until the “numeric tower” is nailed down.

+
+

rrest

+

Function

+
   [a b ...] rrest
+---------------------
+        [...]
+

Definition

+
+

rest rest

+
+ +

rest

+
+

rshift

+

Basis Function

+

Logical Right-Shift

+
   a n rshift
+----------------
+     (a∕2ⁿ)
+ +

lshift

+
+

run

+

Function

+

Run a quoted program in a list.

+

Example

+
   [1 2 +] run
+-----------------
+       [3]
+

Definition

+
+

<{} infra

+
+
+

second

+

Function

+
   [a b ...] second
+----------------------
+          b
+

Definition

+
+

rest first

+
+ +

first third fourth

+
+

select

+

Basis Function

+

Use a Boolean value to select one of two items from a sequence. :

+
   [a b] false select
+------------------------
+           a
+
+   [a b] true select
+-----------------------
+           b
+

Discussion

+

The sequence can contain more than two items but not fewer.

+ +

choice

+
+

sharing

+

Function

+

Print redistribution information.

+

Discussion

+

Mathematically this is a form of id, but it has the side-effect of printing out the GPL notice.

+ +

warranty

+
+

shift

+

Function

+

Move the top item from one list to another.

+

Example

+
   [x y z] [a b c] shift
+---------------------------
+      [a x y z] [b c]
+

Definition

+
+

uncons [swons] dip

+
+ +

shunt

+
+

shunt

+

Function

+

Like concat but reverse the top list into the second.

+

Example

+
   [a b c] [d e f] shunt
+---------------------------
+       [f e d a b c]
+

Definition

+
+

[swons] step

+
+

Discussion

+

This is more efficient than concat so prefer it if you don’t need to preserve order.

+ +

concat reverse shift

+
+

size

+

Function

+

Replace a list with its size.

+

Example

+
   [23 [cats] 4] size
+------------------------
+           3
+

Definition

+
+

[pop ++] step_zero

+
+
+

sort

+

Function

+

Given a list return it sorted.

+

Example

+
   [4 2 5 7 1] sort
+----------------------
+      [1 2 4 5 7]
+
+

spiral_next

+

Function

+

Example code.

+

Discussion

+

See the “Square Spiral Example Joy Code” notebook.

+
+

split_at

+

Function

+

Split a list (second on the stack) at the position given by the number on the top of the stack.

+

Example

+
   [1 2 3 4 5 6 7] 4 split_at
+--------------------------------
+       [5 6 7] [4 3 2 1]
+

Definition

+
+

[drop] [take] clop

+
+

Discussion

+

Take a list and a number n from the stack, take n items from the top of the list and shunt them onto a new list that replaces the number n on the top of the stack.

+ +

split_list

+
+

split_list

+

Function

+

Split a list (second on the stack) at the position given by the number on the top of the stack such that concat would reconstruct the original list.

+
   [1 2 3 4 5 6 7] 4 split_list
+----------------------------------
+        [1 2 3 4] [5 6 7]
+

Definition

+
+

[take reverse] [drop] clop

+
+

Discussion

+

Compare with split_at. This function does extra work to ensure that concat would reconstruct the original list.

+ +

split_at

+
+

sqr

+

Function

+

Square the number on the top of the stack.

+
   n  sqr
+------------
+     n²
+

Definition

+
+

dup mul

+
+
+

sqrt

+

Basis Function Combinator

+

Return the square root of the number a. Negative numbers return complex roots.

+

Discussion

+

Another “numeric tower” hatch…

+
+

stack

+

Function

+

Put the stack onto the stack.

+
      ... c b a stack
+---------------------------
+   ... c b a [a b c ...]
+

Definition

+
+

[] swaack dup swaack first

+
+

Discussion

+

This function forms a pair with [unstack], and together they form the complement to the “destructive” pair enstacken and disenstacken.

+ +

[unstack] enstacken disenstacken

+
+

stackd

+

Function

+

Grab the stack under the top item and put it onto the stack.

+

Example

+
   ... 1 2 3 stackd
+------------------------
+  ... 1 2 [2 1 ...] 3
+

Definition

+
+

[stack] dip

+
+
+

step

+

Combinator

+

Run a quoted program on each item in a sequence.

+
   ... [] [Q] step
+---------------------
+         ...
+
+
+   ... [a] [Q] step
+----------------------
+      ... a Q
+
+
+   ... [a b c] [Q] . step
+----------------------------------------
+             ... a . Q [b c] [Q] step
+

Discussion

+

See the Recursion Combinators notebook.

+ +

step_zero

+
+

step_zero

+

Combinator

+

Like step but with 0 as the initial value.

+
   [...] [F] step_zero
+-------------------------
+     0 [...] [F] step
+

Definition

+
+

0 roll> step

+
+

Discussion

+

size and sum can both be defined in terms of this specialization of step.

+ +

step

+
+

stuncons

+

Function

+

Take the stack and uncons the top item.

+

Example

+
   1 2 3 stuncons
+--------------------
+   1 2 3 3 [2 1]
+

Definition

+
+

stack uncons

+
+
+

stununcons

+

Function

+

Take the stack and uncons the top two items.

+

Example

+
   1 2 3 stununcons
+----------------------
+    1 2 3 3 2 [1]
+

Definition

+
+

stack uncons uncons

+
+ +

stuncons

+
+

sub

+

Basis Function

+

Subtract the number on the top of the stack from the number below it.

+
   a b sub
+-------------
+    (a-b)
+ +

add

+
+

succ

+

Function

+

Successor. Increment TOS.

+

Definition

+
+

1 +

+
+ +

pred

+
+

sum

+

Combinator

+

Given a quoted sequence of numbers return the sum.

+

Example

+
   [1 2 3 4 5] sum
+---------------------
+         15
+

Definition

+
+

[+] step_zero

+
+ +

size

+
+

swaack

+

Basis Function

+

Swap stack. Take a list from the top of the stack, replace the stack with the list, and put the old stack onto it.

+

Example

+
   1 2 3 [4 5 6] swaack
+--------------------------
+   6 5 4 [3 2 1]
+

Discussion

+

This function works as a kind of “context switch”. It’s used in the definition of infra.

+ +

infra

+
+

swap

+

Basis Function

+

Swap the top two items on the stack.

+
   a b swap
+--------------
+     b a
+ +

swapd

+
+

swapd

+

Function

+

Swap the second and third items on the stack.

+
   a b c swapd
+-----------------
+      b a c
+

Definition

+
+

[swap] dip

+
+ +

over tuck

+
+

swoncat

+

Function

+

concat two lists, but swap the lists first.

+

Definition

+
+

swap concat

+
+ +

concat

+
+

swons

+

Function

+

Like cons but swap the item and list.

+
   [...] a swons
+-------------------
+      [a ...]
+

Definition

+
+

swap cons

+
+
+

tailrec

+

Combinator

+

A specialization of the genrec combinator.

+

Definition

+
+

[i] genrec

+
+

Discussion

+

Some recursive functions do not need to store additional data or pending actions per-call. These are called “tail recursive” functions. In Joy, they appear as genrec definitions that have i for the second half of their recursive branch.

+

See the Recursion Combinators notebook.

+ +

genrec

+
+

take

+

Function

+

Expects an integer n and a list on the stack and replace them with a list with just the top n items in reverse order.

+
   [a b c d] 2 take
+----------------------
+        [b a]
+

Definition

+
+

<<{} [shift] times pop

+
+
+

ternary

+

Combinator

+

Run a quoted program using exactly three stack values and leave the first item of the result on the stack.

+
   ... z y x [P] ternary
+-------------------------
+         ... a
+

Definition

+
+

binary popd

+
+

Discussion

+

Runs any other quoted function and returns its first result while consuming exactly three items from the stack.

+ +

binary nullary unary

+
+

third

+

Function

+
   [a b c ...] third
+-----------------------
+           c
+

Definition

+
+

rest second

+
+ +

first second fourth rest

+
+

times

+

Combinator

+

Expect a quoted program and an integer n on the stack and do the program n times.

+
   ... n [Q] . times
+-----------------------  w/ n <= 0
+         ... .
+
+   ... 1 [Q] . times
+-----------------------
+         ... . Q
+
+   ... n [Q] . times
+-------------------------------------  w/ n > 1
+         ... . Q (n-1) [Q] times
+

Definition

+
+

[-- dip] cons [swap] infra [0 >] swap while pop :

+
+

Discussion

+

This works by building a little while program and running it:

+
                 1 3 [++] • [-- dip] cons [swap] infra [0 >] swap while pop                                                                                                                 
+        1 3 [++] [-- dip] • cons [swap] infra [0 >] swap while pop                                                                                                                          
+        1 3 [[++] -- dip] • [swap] infra [0 >] swap while pop                                                                                                                               
+ 1 3 [[++] -- dip] [swap] • infra [0 >] swap while pop                                                                                                                                      
+              dip -- [++] • swap [3 1] swaack [0 >] swap while pop                                                                                                                          
+              dip [++] -- • [3 1] swaack [0 >] swap while pop                                                                                                                               
+        dip [++] -- [3 1] • swaack [0 >] swap while pop                                                                                                                                     
+        1 3 [-- [++] dip] • [0 >] swap while pop                                                                                                                                            
+  1 3 [-- [++] dip] [0 >] • swap while pop                                                                                                                                                  
+  1 3 [0 >] [-- [++] dip] • while pop
+

This is a common pattern in Joy. You accept some parameters from the stack which typically include qouted programs and use them to build another program which does the actual work. This is kind of like macros in Lisp, or preprocessor directives in C.

+
+

truthy

+

See bool.

+
+

tuck

+

Function

+

dup the item on the top of the stack under the second item on the stack.

+
   a b tuck
+--------------
+    b a b
+

Definition

+
+

dup [swap] dip

+
+ +

over

+
+

unary

+

(Combinator)

+

Run a quoted program using exactly one stack value and leave the first item of the result on the stack.

+
   ... x [P] unary
+---------------------
+       ... a
+

Definition

+
+

nullary popd

+
+

Discussion

+

Runs any other quoted function and returns its first result while consuming exactly one item from the stack.

+ +

binary nullary ternary

+
+

uncons

+

Basis Function

+

Removes an item from a list and leaves it on the stack under the rest of the list. You cannot uncons an item from an empty list.

+
   [a ...] uncons
+--------------------
+      a [...]
+

Discussion

+

This is the inverse of cons.

+ +

cons

+
+

unique

+

Function

+

Given a list remove duplicate items.

+
+

unit

+

Function

+
   a unit
+------------
+    [a]
+

Definition

+
+

[] cons

+
+
+

unquoted

+

Combinator

+

Unquote (using i) the list that is second on the stack.

+

Example

+
   1 2 [3 4] 5 unquoted
+--------------------------
+         1 2 3 4 5
+

Definition

+
+

[i] dip

+
+ +

unit

+
+

unswons

+

Function

+
   [a ...] unswons
+---------------------
+       [...] a
+

Definition

+
+

uncons swap

+
+
+

void

+

Basis Function

+

True if the form on TOS is void otherwise False.

+

Discussion

+

A form is any Joy expression composed solely of lists. This represents a binary Boolean logical formula in the arithmetic of the “Laws of Form”, see The Markable Mark

+
+

warranty

+

Basis Function

+

Print warranty information.

+
+

while

+

Combinator

+

A specialization of loop that accepts a quoted predicate program P and runs it nullary.

+
   [P] [F] while
+------------------- P -> false
+
+    [P] [F] while
+--------------------- P -> true
+   F [P] [F] while
+

Definition

+
+

swap nulco dupdipd concat loop

+
+ +

loop

+
+

words

+

Basis Function

+

Print all the words in alphabetical order.

+

Discussion

+

Mathematically this is a form of id.

+ +

help

+
+

x

+

Combinator

+

Take a quoted function F and run it with itself as the first item on the stack.

+
   [F] x
+-----------
+   [F] F
+

Definition

+
dup i
+

Discussion

+

The simplest recursive pattern.

+

See the Recursion Combinators notebook. as well as Recursion Theory and Joy by Manfred von

+
+

xor

+

Basis Function

+

Logical bit-wise eXclusive OR.

+ +

and or

+
+

zip

+

Function

+

Replace the two lists on the top of the stack with a list of the pairs from each list. The smallest list sets the length of the result list.

+

Example

+
   [1 2 3] [4 5 6] zip
+-------------------------
+   [[4 1] [5 2] [6 3]]
+ + diff --git a/docs/html/index.html b/docs/html/index.html index ae68769..f3aea0f 100644 --- a/docs/html/index.html +++ b/docs/html/index.html @@ -33,14 +33,14 @@ Joy and its deeper facets as well as how to program in it and several interesting aspects. It's quite a treasure trove.

Example Code

Here is an example of Joy code:

-
[   [[abs] ii <=]
-    [
-        [<>] [pop !-] ||
-    ] &&
-]
-[[    !-] [[++]] [[--]] ifte dip]
-[[pop !-]  [--]   [++]  ifte    ]
-ifte
+
square_spiral ≡ [_p] [_then] [_else] ifte
+
+_p  ≡ [_p0] [_p1] &&
+_p0 ≡ [abs] ii <=
+_p1 ≡ [<>] [pop !-] ||
+
+_then ≡ [    !-] [[++]] [[--]] ifte dip
+_else ≡ [pop !-]  [--]   [++]  ifte
 

 
It might seem unreadable but with a little familiarity it becomes just as legible as any other notation.

 
This function accepts two integers on the stack and increments or
@@ -88,8 +88,8 @@ coordinate pair in a square spiral (like the kind used to construct an
 
Jupyter Notebooks

 
Notebooks

 
The docs/notebooks dir contains Jupyter notebooks, ... TODO

-
Function Reference

-
Function Reference

+
Function Reference

+
Function Reference

 
Building the Docs

 
Run make in the docs directory.

 
Basics of Joy

diff --git a/docs/reference/grabN.md b/docs/reference/grabN.md
index 0b2455d..a20495a 100644
--- a/docs/reference/grabN.md
+++ b/docs/reference/grabN.md
@@ -4,7 +4,7 @@
 
 Function
 
-Expect a number on the top of the satck and put that many items from uner it onto a new list.
+Expect a number on the top of the stack and [cons] that many items from under it onto a new list.
 
 ### Example
 
diff --git a/docs/reference/mkref/FuncRef.html b/docs/reference/mkref/FuncRef.html
index bf874f1..9d7ed40 100644
--- a/docs/reference/mkref/FuncRef.html
+++ b/docs/reference/mkref/FuncRef.html
@@ -4,7 +4,7 @@
   
   
   
-  Functor Reference
+  Function Reference