definition module check

from StdOverloaded import class toString
from Data.Either import :: Either
from ast import :: Function, :: Expression

:: Scheme = Forall [[Char]] Type
:: Type = TVar [Char] | TInt | TBool | (-->) infixr 9 Type Type

instance toString Scheme, Type

check :: [Function] -> Either [String] (Expression, [([Char], Scheme)])