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(* Title: HOL/Lex/RegExp.thy
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ID: $Id$
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Author: Tobias Nipkow
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Copyright 1998 TUM
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Regular expressions
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*)
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RegExp = RegSet +
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datatype 'a rexp = Empty
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| Atom 'a
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| Union ('a rexp) ('a rexp)
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| Conc ('a rexp) ('a rexp)
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| Star ('a rexp)
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consts lang :: 'a rexp => 'a list set
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primrec
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"lang Empty = {}"
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"lang (Atom a) = {[a]}"
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"lang (Union el er) = (lang el) Un (lang er)"
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"lang (Conc el er) = RegSet.conc (lang el) (lang er)"
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"lang (Star e) = RegSet.star(lang e)"
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end
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