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Allow reverse iteration of lowercase'd/uppercase'd chars by spektom · Pull Reque...

 2 years ago
source link: https://github.com/rust-lang/rust/pull/88858
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The PR implements DoubleEndedIterator trait for ToLowercase and ToUppercase.

This enables reverse iteration of lowercase/uppercase variants of character sequences.
One of use cases: determining whether a char sequence is a suffix of another one.

Example:

fn endswith_ignore_case(s1: &str, s2: &str) -> bool {
    for eob in s1
        .chars()
        .flat_map(|c| c.to_lowercase())
        .rev()
        .zip_longest(s2.chars().flat_map(|c| c.to_lowercase()).rev())
    {
        match eob {
            EitherOrBoth::Both(c1, c2) => {
                if c1 != c2 {
                    return false;
                }
            }
            EitherOrBoth::Left(_) => return true,
            EitherOrBoth::Right(_) => return false,
        }
    }
    true
}

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