@@ -0,0 +1,593 @@
+class Binop:%0A    def __init__(self, op, left, right):%0A        self.op = op%0A        self.left = left%0A        self.right = right%0A        %0A    def eval(self, env):%0A        lval = self.left.eval(env)%0A        rval = self.right.eval(env)%0A        if self.op == %22+%22:%0A            val = lval + rval%0A        elif self.op == %22-%22:%0A            val = lval - rval%0A        elif self.op == %22*%22:%0A            val = lval * rval%0A        elif self.op == %22/%22:%0A            val = lval / rval%0A        return val%0A        %0A    def __repr__(self):%0A        return %22Binop: %7B0%7D %7B1%7D %7B2%7D%22.format(self.left, self.op, self.right)%0A

Create binop.py