# { dg-options "-fstropping=upper" }  #
BEGIN PROC is even = (INT n) BOOL: (n = zero | TRUE | is odd (DECR n));
      PROC is odd = (INT n) BOOL: (n = zero | FALSE | is even (DECR n));
      OP DECR = (INT a) INT:  a - 1;
      ASSERT (is even (20));
      ASSERT (is odd (13));
      INT zero := 0;
      SKIP
END