Joy (programming language)
This article possibly contains original research. (May 2009) |
Developer | Manfred von Thun John Cowan |
---|---|
First appeared | 2001 |
Stable release | March 17, 2003
/ March 17, 2003 |
dynamic | |
Major implementations | |
Joy0, Joy1, "Current Joy", "John Cowan's Joy", "JoyJ (Joy in jvmm)" | |
Influenced by | |
Scheme, FP, Forth | |
Influenced | |
Factor, Cat, V, Trith |
The Joy programming language in
How it works
Joy is unusual among functional programming languages (except for
int square(int x)
{
return x * x;
}
The variable x is a parameter which is replaced by the argument to be squared when the function is called.
In a functional language (Scheme), the same function could be defined:
(define square
(lambda (x)
(* x x)))
This is different in many ways, but it still uses the parameter x in the same way.
In Joy, the square function is defined:
DEFINE square == dup * .
In Joy, everything is a function that takes a
- The dup operator simply duplicates the top element of the stack by pushing a copy of it.
- The * operator pops two numbers off the stack and pushes their product.
So the square function makes a copy of the top element, and then multiplies the two top elements of the stack, leaving the square of the original top element at the top of the stack, with no need for a formal parameter. This makes Joy concise, as illustrated by this definition of quicksort:
DEFINE qsort == [small] [] [uncons [>] split] [enconcat] binrec.
"binrec" is one of Joy's many
- the termination condition (if a list is "small" (1 or 0 elements) it is already sorted),
- what to do if the termination condition is met (in this case nothing),
- what to do by default (split the list into two halves by comparing each element with the pivot), and finally
- what to do at the end (insert the pivot between the two sorted halves).
Mathematical purity
In Joy, the
Joy is a concatenative programming language: "The concatenation of two programs denotes the composition of the functions denoted by the two programs".[2]
Its library routines mirror those of ISO C, though the current implementation is not easily extensible with functions written in C.
See also
References
- ^ Manfred von Thun (December 12, 2003). "A Conversation with Manfred von Thun". Retrieved May 31, 2013.
In the early 1980s I came across the famous Backus paper "Can programming be liberated from the von Neumann style," and I was immediately intrigued by the higher level of programming in his FP.
- ^ "Mathematical Foundations of Joy". Archived from the original on October 7, 2011.
External links
- Official Joy Programming Language Website (La Trobe University) at the Wayback Machine (archived 2012-09-07)
- ZIP of Official Joy Programming Language Website (La Trobe University)
- Joy homepage mirror
- Joy source code (GitHub-Archive)
- .
- von Thun, Manfred; Thomas, Reuben (October 9, 2001). "Joy: Forth's Functional Cousin" (PDF). Proceedings of the 17th EuroForth Conference.
- Christopher Diggins (December 31, 2008). "What is a Concatenative Language". Dr. Dobbs.
- Apter, Stevan. "Functional Programming in Joy and K". Vector. Archived from the original on 2008-08-28. Retrieved 2011-02-28.
- mjoy, an interpreter in Lazarus for drawings with turtle graphics (Subset of Joy)