Multiple return values. In Rust programs we often return multiple values—a tuple creation expression can be used. Strings, integers, and even vectors can be returned.
Omit return keyword. Rust is an expression-based language. Because of this, was can omit the return keyword as the last expression in a function is automatically returned.
Detail We call get_info in 2 ways. We can access the tuple itself, and then get its 0 and 1 fields.
Finally We can unpack the fist and second items from the tuple returned by get_info in a single statement, for the most elegant code.
fn get_info(value: &str) -> (i32, usize) {
// Return tuple of 2 values based on result of if-statement.
if value == "bird" {
(100, 500)
} else {
(-1, 600)
}
}
fn main() {
let result = get_info("bird");
let first = result.0;
let second = result.1;
println!("{} {}", first, second);
// Unpack the 2 values in a single statement.
let (first, second) = get_info("?");
println!("{} {}", first, second);
}100 500
-1 600
Performance notes. In Rust, tuples are not garbage-collected so they have minimal overhead. They are even allocated on the stack, making them as fast as other types like usize.
So Returning multiple values with tuples can be done even in performance-critical code. It is a zero-cost abstraction.
A summary. With tuple syntax, multiple values can be returned in Rust programs. This is elegant, easy to read, and as a zero-cost abstraction is fast.
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This page was last updated on Feb 26, 2023 (edit link).