diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
commit | 26a029d407be480d791972afb5975cf62c9360a6 (patch) | |
tree | f435a8308119effd964b339f76abb83a57c29483 /third_party/rust/itertools/src/minmax.rs | |
parent | Initial commit. (diff) | |
download | firefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz firefox-26a029d407be480d791972afb5975cf62c9360a6.zip |
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/rust/itertools/src/minmax.rs')
-rw-r--r-- | third_party/rust/itertools/src/minmax.rs | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/third_party/rust/itertools/src/minmax.rs b/third_party/rust/itertools/src/minmax.rs new file mode 100644 index 0000000000..52b2f115dd --- /dev/null +++ b/third_party/rust/itertools/src/minmax.rs @@ -0,0 +1,115 @@ + +/// `MinMaxResult` is an enum returned by `minmax`. +/// +/// See [`.minmax()`](crate::Itertools::minmax) for more detail. +#[derive(Copy, Clone, PartialEq, Debug)] +pub enum MinMaxResult<T> { + /// Empty iterator + NoElements, + + /// Iterator with one element, so the minimum and maximum are the same + OneElement(T), + + /// More than one element in the iterator, the first element is not larger + /// than the second + MinMax(T, T) +} + +impl<T: Clone> MinMaxResult<T> { + /// `into_option` creates an `Option` of type `(T, T)`. The returned `Option` + /// has variant `None` if and only if the `MinMaxResult` has variant + /// `NoElements`. Otherwise `Some((x, y))` is returned where `x <= y`. + /// If the `MinMaxResult` has variant `OneElement(x)`, performing this + /// operation will make one clone of `x`. + /// + /// # Examples + /// + /// ``` + /// use itertools::MinMaxResult::{self, NoElements, OneElement, MinMax}; + /// + /// let r: MinMaxResult<i32> = NoElements; + /// assert_eq!(r.into_option(), None); + /// + /// let r = OneElement(1); + /// assert_eq!(r.into_option(), Some((1, 1))); + /// + /// let r = MinMax(1, 2); + /// assert_eq!(r.into_option(), Some((1, 2))); + /// ``` + pub fn into_option(self) -> Option<(T,T)> { + match self { + MinMaxResult::NoElements => None, + MinMaxResult::OneElement(x) => Some((x.clone(), x)), + MinMaxResult::MinMax(x, y) => Some((x, y)) + } + } +} + +/// Implementation guts for `minmax` and `minmax_by_key`. +pub fn minmax_impl<I, K, F, L>(mut it: I, mut key_for: F, + mut lt: L) -> MinMaxResult<I::Item> + where I: Iterator, + F: FnMut(&I::Item) -> K, + L: FnMut(&I::Item, &I::Item, &K, &K) -> bool, +{ + let (mut min, mut max, mut min_key, mut max_key) = match it.next() { + None => return MinMaxResult::NoElements, + Some(x) => { + match it.next() { + None => return MinMaxResult::OneElement(x), + Some(y) => { + let xk = key_for(&x); + let yk = key_for(&y); + if !lt(&y, &x, &yk, &xk) {(x, y, xk, yk)} else {(y, x, yk, xk)} + } + } + } + }; + + loop { + // `first` and `second` are the two next elements we want to look + // at. We first compare `first` and `second` (#1). The smaller one + // is then compared to current minimum (#2). The larger one is + // compared to current maximum (#3). This way we do 3 comparisons + // for 2 elements. + let first = match it.next() { + None => break, + Some(x) => x + }; + let second = match it.next() { + None => { + let first_key = key_for(&first); + if lt(&first, &min, &first_key, &min_key) { + min = first; + } else if !lt(&first, &max, &first_key, &max_key) { + max = first; + } + break; + } + Some(x) => x + }; + let first_key = key_for(&first); + let second_key = key_for(&second); + if !lt(&second, &first, &second_key, &first_key) { + if lt(&first, &min, &first_key, &min_key) { + min = first; + min_key = first_key; + } + if !lt(&second, &max, &second_key, &max_key) { + max = second; + max_key = second_key; + } + } else { + if lt(&second, &min, &second_key, &min_key) { + min = second; + min_key = second_key; + } + if !lt(&first, &max, &first_key, &max_key) { + max = first; + max_key = first_key; + } + } + } + + MinMaxResult::MinMax(min, max) +} |