Dab solver - Metavariable

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Attempts to formalize the notion of metavariable result in some kind of [[type theory]].^ref

In [[computing]] one often needs to specify and document the syntax and semantics of a [[computer language]], more or less formally. A term often used for metavariable in that area is "[[metasyntactic variable]]". Furthermore, because of the common practice in [[hacker culture]] to use [[nonsense word]]s like "[[foo]]" as metavariables, the term "metasyntactic variable"  such words by themselves; for instance, "foo" is referred to as "the first metasyntactic variable" in the first edition of [[The Hacker's Dictionary]].

==  See also  ==

* [[Explicit substitution]]

== References ==

{{Reflist}}

[[Category:Metalogic]]
[[Category:Variables]]
[[Category:Syntax (logic)]]
[[Category:Logic symbols]]

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{{for|the term as used in computer science and hacking culture|Metasyntactic variable}}
In [[logic]], a '''metavariable''' (also '''metalinguistic variable'''<ref>[[Geoffrey Hunter (logician)|Geoffrey Hunter]], ''Metalogic: An Introduction to the Metatheory of Standard First-Order Logic'' p.13</ref> or '''syntactical variable'''<ref>{{Citation | page = 7 | last1=Shoenfield | first1=Joseph R. | title=Mathematical Logic | origyear=1967 | publisher=[[A K Peters]] | edition=2nd | isbn=978-1-56881-135-2 | year=2001}}</ref>) is a [[symbol (formal)|symbol]] or symbol string which belongs to a [[metalanguage]] and stands for elements of some [[object language]]. For instance, in the sentence

:''Let '''A''' and '''B''' be two sentences of a language ℒ''

the symbols '''A''' and '''B''' are part of the metalanguage in which the statement about the object language ℒ is formulated.

[[John Corcoran (logician)|John Corcoran]] considers this terminology unfortunate because it obscures the use of [[schema (logic)|schema]]ta and because such "variables" do not actually range over a domain.<ref>Corcoran, J. 2006. Schemata: the Concept of Schema in the History of Logic. ''Bulletin of Symbolic Logic'' 12: 219-40</ref>{{rp|220|date=November 2012}}

The convention is that a metavariable is to be uniformly substituted with the same instance in all its appearances in a given schema. This is in contrast with [[nonterminal]] symbols in [[formal grammars]] where the nonterminals on the right of a production can be substituted by different instances.<ref name="Tennent2002">{{cite book|author=R. D. Tennent|title=Specifying Software: A Hands-On Introduction|year=2002|publisher=Cambridge University Press|isbn=978-0-521-00401-5|pages=36-37 and 210}}</ref>

Attempts to formalize the notion of metavariable result in some kind of [[type theory]].<ref>Masahiko Sato, Takafumi Sakurai, Yukiyoshi Kameyama, and Atsushi Igarashi. "[http://www.sato.kuis.kyoto-u.ac.jp/~masahiko/papers/csl-03.ps Calculi of Meta-variables]" in ''Computer Science Logic. 17th International Workshop CSL 2003. 12th Annual Conference of the [[EACSL]]. 8th Kurt Gödel Colloquium, KGC 2003, Vienna, Austria, August 25-30, 2003. Proceedings'', Springer [[Lecture Notes in Computer Science]] 2803. ISBN 3-540-40801-0. pp. 484–497</ref>

In [[computing]] one often needs to specify and document the syntax and semantics of a [[computer language]], more or less formally. A term often used for metavariable in that area is "[[metasyntactic variable]]". Furthermore, because of the common practice in [[hacker culture]] to use [[nonsense word]]s like "[[foo]]" as metavariables, the term "metasyntactic variable" <<link:0>> such words by themselves; for instance, "foo" is referred to as "the first metasyntactic variable" in the first edition of ''[[The Hacker's Dictionary]]''.

== See also ==
* [[Explicit substitution]]

==References==
{{Reflist}}

[[Category:Metalogic]]
[[Category:Variables]]
[[Category:Syntax (logic)]]
[[Category:Logic symbols]]

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Dab solver - Metavariable

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