6.6 KiB
Thun
A Dialect of Joy.
version 0.5.0
Simple pleasures are the best.
Joy is a programming language created by Manfred von Thun that is easy to use and understand and has many other nice properties. This project implements interpreters for a dialect that attempts to stay very close to the spirit of Joy but does not precisely match the behaviour of the original version written in C.
Joy is:
The best source (no pun intended) for learning about Joy is the information made available at the website of La Trobe University which contains source code for the original C interpreter, Joy language source code for various functions, and a great deal of fascinating material mostly written by Von Thun on 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
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 decrements one of them such that the new pair of numbers is the next coordinate pair in a square spiral (like the kind used to construct an Ulam Spiral ). For more information see Square Spiral Example Joy Code
Project Hosted on OSDN
Directory structure
Thun
|
|-- LICENSE - GPLv3
|-- README.md - this file
|
|-- archive
| |-- Joy-Programming.zip
| `-- README
|
|-- docs
| |-- Makefile - Generate https://joypy.osdn.io/ site.
| |-- notebooks - Jupyter Notebooks and supporting modules
| |-- reference - Docs for each function.
| |-- dep-graphs - Generated dependency graphs.
| `-- README - Table of Contents
|
`-- implementations
|
|-- Nim - interpreter
|
|-- Prolog - interpreter
| type inference
| work-in-progress compiler
|
|-- Python - interpreter
|
`-- defs.txt - common Joy definitions for all interpreters
Documentation
Jupyter Notebooks
The docs/notebooks dir contains Jupyter notebooks, ... TODO
Function Reference
Building the Docs
Run make in the docs directory.
Basics of Joy
Joy is stack-based. There is a main stack that holds data items: integers, bools, symbols, and sequences or quotes which hold data items themselves.
23 dup [21 18 /] [1 [2 [3]]]
A Joy expression is just a sequence (a.k.a. "list") of items. Sequences intended as programs are called "quoted programs". Evaluation proceeds by iterating through the terms in the expression, putting all literals onto the main stack and executing functions as they are encountered. Functions receive the current stack and return the next stack.
Literals and Simple Functions
joy? 1 2 3
. 1 2 3
1 . 2 3
1 2 . 3
1 2 3 .
1 2 3 <-top
joy? + +
1 2 3 . + +
1 5 . +
6 .
6 <-top
joy? 7 *
6 . 7 *
6 7 . *
42 .
42 <-top
joy?
Combinators
The main loop is very simple as most of the action happens through what are called "combinators": functions which accept quoted programs on the stack and run them in various ways. These combinators factor specific patterns that provide the effect of control-flow in other languages (such as ifte which is like if..then..else..) Combinators receive the current expession in addition to the stack and return the next expression. They work by changing the pending expression the interpreter is about to execute. The combinators could work by making recursive calls to the interpreter and all intermediate state would be held in the call stack of the implementation language, in this joy implementation they work instead by changing the pending expression and intermediate state is put there.
joy? 23 [0 >] [dup --] while
...
-> 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
TODO:
§.4.4 Definitions and More Elaborate Functions
§.4.5 Programming and Metaprogramming
§.4.6 Refactoring
§.6 References & Further Reading
Homepage at La Trobe University
Misc...
Stack based - literals (as functions) - functions - combinators - Refactoring and making new definitions - traces and comparing performance - metaprogramming as programming, even the lowly integer range function can be expressed in two phases: building a specialized program and then executing it with a combinator - ?Partial evaluation?
- ?memoized dynamic dependency graphs? - algebra
Copyright © 2014-2022 Simon Forman
This file is part of Thun
Thun is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
Thun is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with Thun. If not see http://www.gnu.org/licenses/.