CS 386L Programming Assignment (HW 6)

Implement type inference for a language with
     * variables, lambda functions, application
     * let binding
     * integers, boolean, binary integer & boolean operators
     * recursive values declaration
Implement Let polymorphism, using the algorithm defined on pages 333-334.
Implement a few basic operations on data types, including
  multiplication, addition, equality
Use the State monad to collect your constraints
Implement the unification algorithm 
Define Show instances for your data types to output the results using a pleasant notation

Use the following type definitions

type X = String

data Type = TInt | TBool | Fun Type Type | TVar X | TPoly [X] Type

data Term = Var X | Lam X Term | App Term Term | Let X Term Term 
        | Rec X Term
	| Num Int | Binary X Term Term