If Expression

# simple form
if (Expr1) {
    Body1
}

# multiple ifs
if (Expr1) {
    Body1
}

else if (Expr2) {
    Body2
}

else if (ExprN) {
    BodyN
}

# if/else
if (Expr1) {
    Body1
}

else {
    ElseBody
}

# if/else if/else
if (Expr1) {
    Body1
}

else if (ExprN) {
    BodyN
}

else {
    ElseBody
}

The branches of an if-expression are scanned sequentially until a guard sequence Expr which evaluates to true is found. Then the corresponding Body (sequence of expressions) is evaluated.

The return value of Body is the return value of the if expression.

If no guard sequence is true, an run-time error will occur.

If necessary, the else branch can be used in the last branch, as that expression is always true.

Note

Parenthesis around conditions are optional

Example:

is_greater_than = fn (X, Y) {
    if X > Y {
        true
    }

    else {
        false
    }
}

Difference Between if and when

if expressions are another way of writting switch statements that avoid the nesting of multiple switchs inside eachother, any boolean expression can be in the Expr of an if expression.

when expressions are a way to write guards in the body of a function, a guard can only contain a subset of expressions that are known to evaluate in constante time, because of that no function calls can be done in the GuardSeq of a when expression.

when expressions are in efene only for compatibility with erlang, the if or switch expressions are recommended.