definition module WhileCommon

from StdOverloaded import class toString, class zero
from GenEq import generic gEq
from Common import ::Either, ::Error
from WhileLexer import ::Token
from Yard import ::Parser

:: Var :== String
:: State :== Var -> Either Error Int

:: Operator = Add | Sub | Mul | Div

:: AExpr = Var Var
         | Lit Int
         | Op AExpr Operator AExpr

:: Comparator = Eq | Ne | Le | Lt | Ge | Gt

:: BExpr = Bool Bool
         | Not BExpr
         | And BExpr BExpr
         | Or BExpr BExpr
         | Comp AExpr Comparator AExpr

derive gEq AExpr, Operator, BExpr, Comparator

instance zero State

instance toString AExpr
instance toString Operator
instance toString BExpr
instance toString Comparator

class run s :: s State -> Either Error State

class eval i o :: i State -> Either Error o
instance eval AExpr Int
instance eval BExpr Bool

class parse o :: [Token] -> Either Error o

paexpr :: Parser Token AExpr
pbexpr :: Parser Token BExpr