else - Rust
Description: API documentation for the Rust `else` keyword in crate `std`.
Keywords: rust, rustlang, rust-lang, else

# [−]Keyword else

What expression to evaluate when an `if` condition evaluates to `false`.

`else` expressions are optional. When no else expressions are supplied it is assumed to evaluate to the unit type `()`.

The type that the `else` blocks evaluate to must be compatible with the type that the `if` block evaluates to.

As can be seen below, `else` must be followed by either: `if`, `if let`, or a block `{}` and it will return the value of that expression.

    let result = if true == false {
        "oh no"
    } else if "something" == "other thing" {
        "oh dear"
    } else if let Some(200) = "blarg".parse::<i32>().ok() {
        "uh oh"
    } else {
        println!("Sneaky side effect.");
        "phew, nothing's broken"
    };

Run

Here's another example but here we do not try and return an expression:

    if true == false {
        println!("oh no");
    } else if "something" == "other thing" {
        println!("oh dear");
    } else if let Some(200) = "blarg".parse::<i32>().ok() {
        println!("uh oh");
    } else {
        println!("phew, nothing's broken");
    }

Run

The above is still an expression but it will always evaluate to `()`.

There is possibly no limit to the number of `else` blocks that could follow an `if` expression however if you have several then a `match` expression might be preferable.

Read more about control flow in the Rust Book.