Editing Conditional (computer programming) (section)

====Rust====
{{Main|Rust (programming language)}}

In [[Rust (programming language)|Rust]], <code>if</code> is always an expression. It evaluates to the value of whichever branch is executed, or to the unit type <code>()</code> if no branch is executed. If a branch does not provide a return value, it evaluates to <code>()</code> by default. To ensure the <code>if</code> expression's type is known at compile time, each branch must evaluate to a value of the same type. For this reason, an <code>else</code> branch is effectively compulsory unless the other branches evaluate to <code>()</code>, because an <code>if</code> without an <code>else</code> can always evaluate to <code>()</code> by default.<ref>{{cite web|title=If and if let expressions|url=https://doc.rust-lang.org/reference/expressions/if-expr.html|access-date=November 1, 2020}}</ref>

<syntaxhighlight lang="rust">
// Assign my_variable some value, depending on the value of x
let my_variable = if x > 20 {
    1
} else {
    2
};

// This variant will not compile because 1 and () have different types
let my_variable = if x > 20 {
    1
};

// Values can be omitted when not needed
if x > 20 {
    println!("x is greater than 20");
}
</syntaxhighlight>