files/practicum/RefactorXX.dcl

   1 definition module RefactorXX
   2
   3 ::      Expr                    = NR   Int
   4                                         | VAR  Name
   5                                         | OP   Expr Operator Expr
   6                                         | LET  Name     Expr Expr
   7 ::      Name              :== String
   8 ::      Operator                = PLUS | MIN | MUL | DIV
   9 ::      Val a                   = Result a | Undef
  10
  11 class fail          c :: c a
  12 class return        c :: a -> c a
  13 class (>>=) infix 0 c :: (c a) (a -> c b) -> c b
  14 class Monad         c | return, >>= c
  15 class MonadFail     c | Monad, fail c
  16
  17 instance fail   [], Val
  18 instance return [], Val
  19 instance >>=    [], Val
  20
  21 from StdClass import class toString
  22
  23 instance toString Expr
  24 free                            :: Expr -> [Name]
  25 remove_unused_lets      :: Expr -> Expr
  26 eval                            :: Expr -> c Int | MonadFail c