How to use AND operator in IF statements in SML
ml, sml, smlnj
Solution
There is no `AND` operator in SML (unless you define one yourself). There is an `and` keyword, but you can't use it inside `if` statements (or generally as a part of any expression) because it's not an operator. It's used in combination with `fun` to define mutually recursive functions.
You're probably looking for the `andalso` operator, which takes two boolean operands and returns true if and only if both operands are true.
Problem
I am new to SML. How do I use the AND operator inside IF statements? Here is my code: ``` val y = 1; val x = 2; if (x = 1 AND y = 2) then print ("YES ") else print("NO "); ``` My error is: stdIn:66.9-67.3 Error: unbound variable or constructor: AND stdIn:66.3-67.9 Error: operator is not a function [literal] operator: int in expression: 1 stdIn:66.3-67.9 Error: operator and operand don't agree [literal] operator domain: bool * bool operand: bool * int in expression: x = (1 ) y = 2 Thank you