A concatenative programming language is a point-free computer

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

in which all expressions denote functions, and the

juxtaposition Juxtaposition is an act or instance of placing two elements close together or side by side. This is often done in order to compare/contrast the two, to show similarities or differences, etc. Speech Juxtaposition in literary terms is the showing ...

of expressions denotes

function composition In mathematics, function composition is an operation that takes two functions and , and produces a function such that . In this operation, the function is applied to the result of applying the function to . That is, the functions and ...

. Concatenative programming replaces function application, which is common in other programming styles, with

as the default way to build

subroutine In computer programming, a function or subroutine is a sequence of program instructions that performs a specific task, packaged as a unit. This unit can then be used in programs wherever that particular task should be performed. Functions may ...

Example

For example, a sequence of operations in an applicative language like the following: y = foo(x) z = bar(y) w = baz(z) ...is written in a concatenative language as a sequence of functions: x foo bar baz Functions and procedures written in concatenative style are not value level, i.e. they typically do not represent the data structures they operate on with explicit names or

identifiers An identifier is a name that identifies (that is, labels the identity of) either a unique object or a unique ''class'' of objects, where the "object" or class may be an idea, physical countable object (or class thereof), or physical noncountable ...

. Instead they are function levela function is defined as a

pipeline Pipeline may refer to: Electronics, computers and computing * Pipeline (computing), a chain of data-processing stages or a CPU optimization found on ** Instruction pipelining, a technique for implementing instruction-level parallelism within a s ...

, or a sequence of operations that take parameters from an implicit

data structure In computer science, a data structure is a data organization, management, and storage format that is usually chosen for efficient access to data. More precisely, a data structure is a collection of data values, the relationships among them, a ...

upon which all functions operate, and return the function results to that shared structure so that it will be used by the next operator. The combination of compositional

semantics Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy Philosophy (f ...

with a

syntax In linguistics, syntax () is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure ( constituency) ...

that mirrors such a semantic makes concatenative languages highly amenable to algebraic manipulation of programs; although it may be difficult to write mathematical expressions directly in them. Concatenative languages can be implemented efficiently with a stack machine, and are commonly present implicitly in

virtual machine In computing, a virtual machine (VM) is the virtualization/emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardw ...

s in the form of their

instruction set In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ' ...

Properties

The properties of concatenative languages are the result of their compositional syntax and semantics: * The reduction of any expression is the simplification of one function to another function; it is never necessary to deal with the application of functions to objects. * Any subexpression can be replaced with a name that represents the same subexpression. This is referred to in the concatenative community as factoring and is used extensively to simplify programs into smaller parts. * The syntax and semantics of concatenative languages form the algebraic structure of a

monoid In abstract algebra, a branch of mathematics, a monoid is a set equipped with an associative binary operation and an identity element. For example, the nonnegative integers with addition form a monoid, the identity element being 0. Monoids ...

. * Concatenative languages can be made well-suited to an implementation inspired by linear logic where no garbage is ever generated.

Implementations

The first concatenative programming language was

Forth Forth or FORTH may refer to: Arts and entertainment * ''forth'' magazine, an Internet magazine * ''Forth'' (album), by The Verve, 2008 * ''Forth'', a 2011 album by Proto-Kaw * Radio Forth, a group of independent local radio stations in Scotla ...

, although

Joy The word joy refers to the emotion evoked by well-being, success, or good fortune, and is typically associated with feelings of intense, long lasting happiness. Dictionary definitions Dictionary definitions of joy typically include a sense of ...

was the first language to call itself concatenative. Other concatenative languages are dc,

Factor Factor, a Latin word meaning "who/which acts", may refer to: Commerce * Factor (agent), a person who acts for, notably a mercantile and colonial agent * Factor (Scotland), a person or firm managing a Scottish estate * Factors of production, suc ...

, Onyx,

PostScript PostScript (PS) is a page description language in the electronic publishing and desktop publishing realm. It is a dynamically typed, concatenative programming language. It was created at Adobe Systems by John Warnock, Charles Geschke, Doug Br ...

, and RPL. Most existing concatenative languages are stack-based; this is not a requirement and other models have been proposed. Concatenative languages are currently used for embedded,

desktop A desktop traditionally refers to: * The surface of a desk (often to distinguish office appliances that fit on a desk, such as photocopiers and printers, from larger equipment covering its own area on the floor) Desktop may refer to various compu ...

, and

web programming Web development is the work involved in developing a website for the Internet (World Wide Web) or an intranet (a private network). Web development can range from developing a simple single static page of plain text to complex web applications, ...

, as target languages, and for research purposes. Most concatenative languages are

dynamically typed In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a type to every "term" (a word, phrase, or other set of symbols). Usually the terms are various constructs of a computer progra ...

. Exceptions include the statically typed Cat language.

References

External links

concatenative.org: A wiki about concatenative languages

Staapl: Forth on Scheme for Embedded Controllers

The Enchilada Programming Language

The Om Programming Language
{{Types of programming languages

Example

Properties

Implementations

See also

References

External links