Concatenative programming language

A concatenative programming language is a point-free computer programming language in which all expressions denote functions, and the juxtaposition of expressions denotes function composition.[1] Concatenative programming replaces function application, which is common in other programming styles, with function composition as the default way to build subroutines.


For example, a sequence of operations in an applicative language like the following:

y = foo(x)
z = bar(y)
w = baz(z) written in a concatenative language as a sequence of functions, without parameters:[2]

foo bar baz

Functions and procedures written in concatenative style are not value level, i.e. they typically don't represent the data structures they operate on with explicit names or identifiers; instead they are function level - a function is defined as a pipeline, a sequence of operations that take parameters from an implicit data structure on which all functions operate, and return the function results to that shared structure so that it will be used by the next operator.[3]

The combination of a compositional semantics with a syntax that mirrors such a semantics makes concatenative languages highly amenable to algebraic manipulation of programs;[4] although it may be difficult to write mathematical expressions directly in them.[5] Concatenative languages can be implemented in an efficient way with a stack machine, and are a common strategy to program virtual machines.[5]

Much of the original work on concatenative language theory was carried out by Manfred von Thun.


The properties of concatenative languages are the result of their compositional syntax and semantics:


The first concatenative programming language was Forth, although Joy was the first language to call itself concatenative. Other concatenative languages are Cat, Enchilada, Factor, Onyx, PostScript, RPL, Staapl, Trith, XY, Kitten, and Om.

Most existing concatenative languages are stack-based; this is not a requirement and other models have been proposed.[9][10][11] Concatenative languages are currently used for embedded, desktop, and web programming, as target languages, and for research purposes.

Most concatenative languages are dynamically typed. One exception is the statically typed Cat language.[12]

See also


  1. "Christopher Diggins: What is a concatenative language". 2008-12-31. Retrieved 2013-07-01.
  2. "Name code not values". Retrieved 13 September 2013.
  3. "Concatenative language". Retrieved 13 September 2013.
  4. "Rationale for Joy, a functional language". Archived from the original on 2011-01-15.
  5. 1 2 "Why Concatenative Programming Matters". Retrieved 13 September 2013.
  6. "von Thun, Manfred: Joy compared with other functional languages". Archived from the original on 2011-10-06.
  7. "von Thun, Manfred: Mathematical foundations of Joy". Archived from the original on 2010-07-31.
  8. "Henry Baker: Linear Logic and Permutation Stacks — The Forth Shall Be First". Retrieved 2013-07-01.
  9. "The Concatenative Language XY". Retrieved 2013-07-01.
  10. "The Enchilada Programming Language". Retrieved 2013-07-01.
  11. "The Om Programming Language". Retrieved 2013-07-01.
  12. "Cat Specification". Archived from the original on 2015-02-05. Retrieved 2013-07-01.

External links

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