private Expr MakeBinaryIntFunctionCall(string functionName, BinaryOperator.Opcode infixOp, Type resultType, Expr lhs, Expr rhs)
{
Function f = verifier.GetOrCreateIntFunction(functionName, infixOp, resultType, lhs.Type, rhs.Type);
var e = new NAryExpr(Token.NoToken, new FunctionCall(f), new List <Expr> {
lhs, rhs
});
e.Type = resultType;
return(e);
}