If expressions and statements

if evaluates a condition and selects one block. The condition must have type Bool.

Basic if

fun checkAccess(allowed: Bool) {
    if allowed {
        println("access granted");
    }
}

Parentheses around the condition are not required:

if count > 0 {
    println("items available");
}

The braces are required. Zap does not convert integers, strings, or pointers to boolean values automatically.

else and else if

fun label(score: Int) String {
    if score >= 90 {
        return "excellent";
    } else if score >= 60 {
        return "pass";
    } else {
        return "retry";
    }
}

Branches are checked in order. The first true condition runs, and the remaining branches are skipped.

Combine conditions

Use &&, ||, and ! to build boolean expressions:

if connected && authenticated {
    println("ready");
}

if !finished || retryable {
    println("run again");
}

The logical operators short-circuit. The right side of && is evaluated only when the left side is true. The right side of || is evaluated only when the left side is false.

Nested branches

fun describe(value: Int) String {
    if value >= 0 {
        if value == 0 {
            return "zero";
        }
        return "positive";
    }
    return "negative";
}

Prefer a guard clause with an early return when nesting would hide the main path:

fun publish(connected: Bool, message: String) Int {
    if !connected {
        return 1;
    }
    if len(message) == 0 {
        return 2;
    }

    println(message);
    return 0;
}

Conditional values

Zap supports the ?: conditional expression when both branches produce compatible values:

var access = authenticated ? "granted" : "denied";
var limit = enabled ? 100 : 0;

Use a statement when a branch performs several actions. Use the expression form when the branch simply chooses a value.

Scope and assignment

Each branch is a block. A variable declared in one branch is not available in the other branch:

if ready {
    var message = "go";
    println(message);
}

// `message` is outside its scope here.

Declare a value before the branch when both paths must update it, and keep its type explicit when the two branches produce different literals.