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progs/app6.scala
author Christian Urban <christian dot urban at kcl dot ac dot uk>
Sun, 12 Oct 2014 19:39:55 +0100
changeset 272 1446bc47a294
parent 262 ee4304bc6350
child 343 539b2e88f5b9
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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def simp(r: Rexp): Rexp = r match {
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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  case ALT(r1, r2) => {
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    val r1s = simp(r1)
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    val r2s = simp(r2)
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    (r1s, r2s) match {
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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      case (NULL, _) => r2s
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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      case (_, NULL) => r1s
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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      case _ => if (r1s == r2s) r1s else ALT(r1s, r2s)
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    }
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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  }
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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  case SEQ(r1, r2) => {
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    val r1s = simp(r1)
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents: 117
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    val r2s = simp(r2)
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    (r1s, r2s) match {
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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      case (NULL, _) => NULL
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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      case (_, NULL) => NULL
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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      case (EMPTY, _) => r2s
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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      case (_, EMPTY) => r1s
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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      case _ => SEQ(r1s, r2s)
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    }
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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  }
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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  case NTIMES(r, n) => NTIMES(simp(r), n)
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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  case r => r
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Christian Urban <urbanc@in.tum.de>
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}
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def ders (s: List[Char], r: Rexp) : Rexp = s match {













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  case Nil => r








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  case c::s => ders(s, simp(der(c, r)))








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}













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