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m Mutual recursion can occur between two *or more* mathematical/computational objects, not just two. This introductory wording in the definition is more consistent with the rest of the article. Tags: Visual edit Mobile edit Mobile web edit |
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{{short description|
<!-- [[WP:NFCC]] violation: [[File:DrawingHands.jpg|thumb|upright|"[[Drawing Hands]]", a drawing by [[M. C. Escher]]]] -->
In [[mathematics]] and [[computer science]], '''mutual recursion''' is a form of [[Recursion (computer science)|recursion]] where two or more mathematical or computational objects, such as functions or datatypes, are defined in terms of each other.<ref>Manuel Rubio-Sánchez, Jaime Urquiza-Fuentes, Cristóbal Pareja-Flores (2002), 'A Gentle Introduction to Mutual Recursion', Proceedings of the 13th annual conference on Innovation and technology in computer science education, June 30–July 2, 2008, Madrid, Spain.</ref> Mutual recursion is very common in [[functional programming]] and in some problem domains, such as [[recursive descent parser]]s, where the datatypes are naturally mutually recursive.
==Examples==
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A more detailed example in [[Scheme (programming language)|Scheme]], counting the leaves of a tree:{{sfn|Harvey|Wright|1999|loc=V. Abstraction: 18. Trees: Mutual Recursion, pp. [https://books.google.com/books?id=igJRhp0KGn8C&pg=PA310&dq=%22mutual%20recursion%22 310–313]}}
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(define (count-leaves tree)
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Some programming styles discourage mutual recursion, claiming that it can be confusing to distinguish the conditions which will return an answer from the conditions that would allow the code to run forever without producing an answer. [[Peter Norvig]] points to a [[design pattern]] which discourages the use entirely, stating:<ref>[http://norvig.com/sudoku.html Solving Every Sudoku Puzzle]</ref>
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==Terminology==
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