Logical Operations

Logical operations combine or invert boolean expressions. They are commonly used in conditions for if, while, and pattern guards.

Operators

let isReady = true;
let hasWork = false;

let shouldRun = isReady && hasWork;  // false
let canWait = isReady || hasWork;    // true
let isBlocked = !isReady;            // false

Logical operands must be boolean values. Numeric values are not accepted as conditions without an explicit comparison:

let count = 3;

if count { }       // error: count is not bool
if count != 0 { }  // valid

Short-Circuit Evaluation

Logical AND and OR evaluate from left to right and short-circuit.

• left && right does not evaluate right when left is false.
• left || right does not evaluate right when left is true.

if index < values.length && values[index] == target {
    Print("found");
}

Here values[index] is evaluated only when index is within the checked range. Short-circuiting also avoids unnecessary function calls:

if IsEnabled() && LoadConfiguration() {
    Start();
}

LoadConfiguration() is called only when IsEnabled() returns true.

Logical NOT

Logical NOT is a unary operator and binds more tightly than comparison, logical AND, and logical OR:

let allowed = !isBlocked && hasPermission;

Parentheses can make a compound negation clearer:

let unavailable = !(isOnline && isReady);

Logical vs. Bitwise

Logical operators short-circuit and operate on truth values. Bitwise operators (&, |, ^, and ~) operate on individual bits and evaluate all operands.

Use &&, ||, and ! for conditions:

if isReady && hasWork {
    Run();
}

Use bitwise operators for masks and packed flags. See Bitwise Operations for &, |, ^, and ~, and Shift Operations for related bit manipulation.

Precedence

Logical NOT has higher precedence than comparisons. Logical AND has higher precedence than logical OR:

let result = !a || b && c;
// Equivalent to: (!a) || (b && c)

See Operator Precedence for the complete precedence table.

See Also

• Comparison Operations — producing the boolean operands
• Bitwise Operations — the non-short-circuiting &, |, ^, ~
• Boolean Types — the bool type these operators consume and produce