From 206f49598e415ba44be1eb60e36ca2a45e5258cd Mon Sep 17 00:00:00 2001
From: Simon Forman <sforman@hushmail.com>
Date: Sat, 20 Jul 2019 19:26:11 -0700
Subject: [PATCH] Add mod, gcd, and hypot; term_expansion for math ops.

---
 thun/defs.txt |  4 +++-
 thun/thun.pl  | 17 +++++++++++++----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/thun/defs.txt b/thun/defs.txt
index 741ba8a..ab0ad81 100644
--- a/thun/defs.txt
+++ b/thun/defs.txt
@@ -9,7 +9,7 @@ average == [sum 1.0 *] [size] cleave /
 b == [i] dip i
 binary == unary popd
 ccons == cons cons
-cleave == fork [popd] dip
+cleave == fork popdd
 codireco == cons dip rest cons
 dinfrirst == dip infrst
 disenstacken == ? [uncons ?] loop pop
@@ -22,7 +22,9 @@ enstacken == stack [clear] dip
 flatten == [] swap [concat] step
 fork == [i] app2
 fourth == rest third
+gcd == true [tuck mod dup 0 >] loop pop
 grba == [stack popd] dip
+hypot == [sqr] ii + sqrt
 ifte == [nullary] dipd swap branch
 ii == [dip] dupdip i
 infra == swons swaack [i] dip swaack
diff --git a/thun/thun.pl b/thun/thun.pl
index 2a14707..0553a71 100644
--- a/thun/thun.pl
+++ b/thun/thun.pl
@@ -44,6 +44,14 @@ term_expansion(comparison_operator(X), (func(X, [A, B|S], [C|S]) :-
 term_expansion(comparison_operator(X, Y), (func(X, [A, B|S], [C|S]) :-
     F =.. [Y, B, A], catch((F -> C=true ; C=false), _, C=F))).
 
+% Likewise for math operators, try to evaluate, otherwise use the symbolic form.
+
+term_expansion(math_operator(X), (func(X, [A, B|S], [C|S]) :-
+    F =.. [X, B, A], catch(C is F, _, C=F))).
+
+term_expansion(math_operator(X, Y), (func(X, [A, B|S], [C|S]) :-
+    F =.. [Y, B, A], catch(C is F, _, C=F))).
+
 
 /*
 An entry point.
@@ -128,10 +136,11 @@ func(dup,     [A|S],  [A, A|S]).
 func(pop,     [_|S],        S ).
 
 % Symbolic math.  Compute the answer, or derivative, or whatever, later.
-func(+, [A, B|S], [B + A|S]).
-func(-, [A, B|S], [B - A|S]).
-func(*, [A, B|S], [B * A|S]).
-func(/, [A, B|S], [B / A|S]).
+math_operator(+).
+math_operator(-).
+math_operator(*).
+math_operator(/).
+math_operator(mod).
 
 % Attempt to calculate the value of a symbolic math expression.
 func(calc, [A|S], [B|S]) :- B is A.