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progs/app52.scala
author Christian Urban <christian.urban@kcl.ac.uk>
Fri, 29 Nov 2024 18:58:18 +0000
changeset 975 ae5c03560d4d
parent 436 9213b8298ca9
permissions -rw-r--r--
update
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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Christian Urban <urbanc@in.tum.de>
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def ders2(s: List[Char], r: Rexp) : Rexp = (s, r) match {
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  case (Nil, r) => r
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  case (s, ZERO) => ZERO
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  case (s, ONE) => if (s == Nil) ONE else ZERO
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  case (s, CHAR(c)) => if (s == List(c)) ONE else
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                       if (s == Nil) CHAR(c) else ZERO
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  case (s, ALT(r1, r2)) => ALT(ders2(s, r2), ders2(s, r2))
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  case (c::s, r) => ders2(s, simp(der(c, r)))
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}
afl-material