Pattern matching: Difference between revisions

Revision as of 03:13, 23 February 2021

Revision as of 22:49, 21 May 2021

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{{aboutAbout|pattern matching in [[functional programming]]||string matching|and|pattern recognition}}

{{forFor|the use of variable matching criteria in defining abstract patterns to match|regular expression}}

{{RefimproveMore citations needed|date=February 2011}}

In [[computer science]], '''pattern matching''' is the act of checking a given '''sequence''' of [[Lexical analysis#Token|tokens]] for the presence of the constituents of some [[pattern]]. In contrast to [[pattern recognition]], the match usually has to be exact: "either it will or will not be a match." The patterns generally have the form of either [[string (computer science)|sequences]] or [[tree structure]]s. Uses of pattern matching include outputting the locations (if any) of a pattern within a token sequence, to output some component of the matched pattern, and to substitute the matching pattern with some other token sequence (i.e., [[Regular expression|search and replace]]).

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The creations of these functions can be automated by Haskell's data [[Record (computer science)|record]] syntax.

This [[Ocaml]] example which defines a [[Red–black_treeRed–black tree|red-black tree]] and a function to re-balance it after element insertion shows how to match on a more complex structure generated by a recursive data type.

<syntaxhighlight lang="ocaml">

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==External links==

{{wikibooksWikibooks|Haskell|Pattern matching}}

{{Commons category}}

{{Commonscat}}

*[http://www.haskell.org/tutorial/patterns.html A Gentle Introduction to Haskell: Patterns]

*[https://archive.is/19990225161739/http://www.haskell.org/development/views.html Views: An Extension to Haskell Pattern Matching]

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{{Strings |state=collapsed}}

{{Authority control}}

{{DEFAULTSORT:Pattern Matching}}