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progs/app05.scala
author Christian Urban <christian.urban@kcl.ac.uk>
Mon, 20 Oct 2025 22:18:21 +0200
changeset 1013 1a23d87d1700
parent 788 3b1136fb6bee
permissions -rw-r--r--
updated
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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def simp(r: Rexp): (Rexp, Val => Val) = r match {
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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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, f1s) = simp(r1)
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    val (r2s, f2s) = 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 (ZERO, _) => (r2s, F_RIGHT(f2s))
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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      case (_, ZERO) => (r1s, F_LEFT(f1s))
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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      case _ =>
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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         if (r1s == r2s) (r1s, F_LEFT(f1s))
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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         else (ALT (r1s, r2s), F_ALT(f1s, f2s))
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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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  ...
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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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def F_RIGHT(f: Val => Val) = (v:Val) => Right(f(v))
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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def F_LEFT(f: Val => Val) = (v:Val) => Left(f(v))
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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def F_ALT(f1: Val => Val, f2: Val => Val) =
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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  (v:Val) => v match {
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    case Right(v) => Right(f2(v))
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Christian Urban <christian dot urban at kcl dot ac dot uk>
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    case Left(v) => Left(f1(v)) }
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