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impl Pattern for char array #86336

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Oct 31, 2021
Merged

impl Pattern for char array #86336

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5e4f212
impl Pattern for char array
camsteffen Jun 15, 2021
28f7890
Add char array without ref Pattern impl
camsteffen Jun 22, 2021
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73 changes: 73 additions & 0 deletions library/core/src/str/pattern.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,8 @@
//! assert_eq!(s.find("you"), Some(4));
//! // char pattern
//! assert_eq!(s.find('n'), Some(2));
//! // array of chars pattern
//! assert_eq!(s.find(&['a', 'e', 'i', 'o', 'u']), Some(1));
//! // slice of chars pattern
//! assert_eq!(s.find(&['a', 'e', 'i', 'o', 'u'][..]), Some(1));
//! // closure pattern
Expand Down Expand Up @@ -79,6 +81,11 @@ use crate::slice::memchr;
/// assert_eq!("abaaa".find('b'), Some(1));
/// assert_eq!("abaaa".find('c'), None);
///
/// // &[char; N]
/// assert_eq!("ab".find(&['b', 'a']), Some(0));
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/// assert_eq!("abaaa".find(&['a', 'z']), Some(0));
/// assert_eq!("abaaa".find(&['c', 'd']), None);
///
/// // &[char]
/// assert_eq!("ab".find(&['b', 'a'][..]), Some(0));
/// assert_eq!("abaaa".find(&['a', 'z'][..]), Some(0));
Expand Down Expand Up @@ -601,6 +608,20 @@ where
}
}

impl<const N: usize> MultiCharEq for [char; N] {
#[inline]
fn matches(&mut self, c: char) -> bool {
self.iter().any(|&m| m == c)
}
}

impl<const N: usize> MultiCharEq for &[char; N] {
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This might be a silly question, but why for &[char; N] instead of for [char; N]?

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Actually that's what I started with, but then I figured this is more flexible/performant for large arrays. Definitely open to discussion on that. Maybe add both?

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I think you do want the reference to solve those bugs where one intends to write a literal &[char] slice pattern, but it's really &[char; N].

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I think both -- ['o', 'l'] for the simple case, and &[...] for the case cuviper mentions.

(I might just delegate both to the impl for slices, though, if there's an easy way to do that.)

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@camsteffen camsteffen Jun 22, 2021 •
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Okay, added both. Unfortunately lifetimes force a lot of separate structs and impls to satisfy into_searcher.

#[inline]
fn matches(&mut self, c: char) -> bool {
self.iter().any(|&m| m == c)
}
}

impl MultiCharEq for &[char] {
#[inline]
fn matches(&mut self, c: char) -> bool {
Expand Down Expand Up @@ -752,6 +773,58 @@ macro_rules! searcher_methods {
};
}

/// Associated type for `<[char; N] as Pattern<'a>>::Searcher`.
#[derive(Clone, Debug)]
pub struct CharArraySearcher<'a, const N: usize>(
<MultiCharEqPattern<[char; N]> as Pattern<'a>>::Searcher,
);

/// Associated type for `<&[char; N] as Pattern<'a>>::Searcher`.
#[derive(Clone, Debug)]
pub struct CharArrayRefSearcher<'a, 'b, const N: usize>(
<MultiCharEqPattern<&'b [char; N]> as Pattern<'a>>::Searcher,
);

/// Searches for chars that are equal to any of the [`char`]s in the array.
///
/// # Examples
///
/// ```
/// assert_eq!("Hello world".find(['l', 'l']), Some(2));
/// assert_eq!("Hello world".find(['l', 'l']), Some(2));
/// ```
impl<'a, const N: usize> Pattern<'a> for [char; N] {
pattern_methods!(CharArraySearcher<'a, N>, MultiCharEqPattern, CharArraySearcher);
}

unsafe impl<'a, const N: usize> Searcher<'a> for CharArraySearcher<'a, N> {
searcher_methods!(forward);
}

unsafe impl<'a, const N: usize> ReverseSearcher<'a> for CharArraySearcher<'a, N> {
searcher_methods!(reverse);
}

/// Searches for chars that are equal to any of the [`char`]s in the array.
///
/// # Examples
///
/// ```
/// assert_eq!("Hello world".find(&['l', 'l']), Some(2));
/// assert_eq!("Hello world".find(&['l', 'l']), Some(2));
/// ```
impl<'a, 'b, const N: usize> Pattern<'a> for &'b [char; N] {
pattern_methods!(CharArrayRefSearcher<'a, 'b, N>, MultiCharEqPattern, CharArrayRefSearcher);
}

unsafe impl<'a, 'b, const N: usize> Searcher<'a> for CharArrayRefSearcher<'a, 'b, N> {
searcher_methods!(forward);
}

unsafe impl<'a, 'b, const N: usize> ReverseSearcher<'a> for CharArrayRefSearcher<'a, 'b, N> {
searcher_methods!(reverse);
}

/////////////////////////////////////////////////////////////////////////////
// Impl for &[char]
/////////////////////////////////////////////////////////////////////////////
Expand Down