progs/app05.scala
changeset 453 36e5752fa191
parent 446 16742bf62365
child 788 3b1136fb6bee
equal deleted inserted replaced
452:b93f4d2aeee1 453:36e5752fa191
     1 def simp(r: Rexp): (Rexp, Val => Val) = r match {
     1 def simp(r: Rexp): (Rexp, Val => Val) = r match {
     2   case ALT(r1, r2) => {
     2   case ALT(r1, r2) => {
     3     val (r1s, f1s) = simp(r1)
     3     val (r1s, f1s) = simp(r1)
     4     val (r2s, f2s) = simp(r2)
     4     val (r2s, f2s) = simp(r2)
     5     (r1s, r2s) match {
     5     (r1s, r2s) match {
     6       case (NULL, _) => (r2s, F_RIGHT(f2s))
     6       case (ZERO, _) => (r2s, F_RIGHT(f2s))
     7       case (_, NULL) => (r1s, F_LEFT(f1s))
     7       case (_, ZERO) => (r1s, F_LEFT(f1s))
     8       case _ => 
     8       case _ => 
     9          if (r1s == r2s) (r1s, F_LEFT(f1s))
     9          if (r1s == r2s) (r1s, F_LEFT(f1s))
    10          else (ALT (r1s, r2s), F_ALT(f1s, f2s)) 
    10          else (ALT (r1s, r2s), F_ALT(f1s, f2s)) 
    11     }
    11     }
    12   }
    12   }