This is the inclusive range operator.
The range x..=y contains all values >= x and <= y, i.e. “from x up to and including y”.
This is in contrast to the non-inclusive range operator x..y, which doesn’t include y itself.
fn main() {
println!("{:?}", (10..20) .collect::<Vec<_>>());
println!("{:?}", (10..=20).collect::<Vec<_>>());
}
// Output:
//
// [10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
// [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
Match expressions
You can also use start..=end as a pattern in a match expression to match any value in the (inclusive) range.
match fahrenheit_temperature {
70..=89 => println!("What lovely weather!"),
_ => println!("Ugh, I'm staying in."),
}
(Using an exclusive range start..end as a pattern is an experimental feature.)
History
Inclusive ranges used to be an experimental nightly-only feature, and were written ... before.
As of Rust 1.26, it’s officially part of the language, and written ..=.
(Before inclusive ranges existed, you actually couldn’t create, say, a range of byte values including 255u8. Because that’d be 0..256, and 256 is out of the u8 range! This is issue #23635.)
See also
- The Rust 1.26 release blog post’s introduction to
..=. - StackOverflow: How do I include the end value in a range?