src/HOL/IMP/Com.thy

proper error message;

header "IMP --- A Simple Imperative Language"

theory Com imports BExp begin

datatype
  com = SKIP 
      | Assign vname aexp       ("_ ::= _" [1000, 61] 61)
      | Seq    com  com         ("_;/ _"  [60, 61] 60)
      | If     bexp com com     ("(IF _/ THEN _/ ELSE _)"  [0, 0, 61] 61)
      | While  bexp com         ("(WHILE _/ DO _)"  [0, 61] 61)

end