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examples for minmax_by and minmax_by_key #1064

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merged 3 commits into from
Oct 9, 2025
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examples for minmax_by and minmax_by_key #1064

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examples for minmax_by and minmax_by_key
Takashiidobe Oct 9, 2025
81ccdfe
simplify examples and use (i32, char) instead of just plain i32 to ma…
Takashiidobe Oct 9, 2025
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code review feedback
Takashiidobe Oct 9, 2025
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55 changes: 48 additions & 7 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4071,17 +4071,17 @@ pub trait Itertools: Iterator {
/// use itertools::Itertools;
/// use itertools::MinMaxResult::{MinMax, NoElements, OneElement};
///
/// let a: [i32; 0] = [];
/// let a: [(i32, char); 0] = [];
/// assert_eq!(a.iter().minmax(), NoElements);
///
/// let a = [1];
/// assert_eq!(a.iter().minmax(), OneElement(&1));
/// let a = [(1, 'a')];
/// assert_eq!(a.iter().minmax(), OneElement(&(1, 'a')));
///
/// let a = [1, 2, 3, 4, 5];
/// assert_eq!(a.iter().minmax(), MinMax(&1, &5));
/// let a = [(0, 'a'), (1, 'b')];
/// assert_eq!(a.iter().minmax(), MinMax(&(0, 'a'), &(1, 'b')));
///
/// let a = [1, 1, 1, 1];
/// assert_eq!(a.iter().minmax(), MinMax(&1, &1));
/// let a = [(1, 'a'), (1, 'b'), (1, 'c')];
/// assert_eq!(a.iter().minmax(), MinMax(&(1, 'a'), &(1, 'c')));
Comment on lines 4074 to 4101
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Please leave them simple numbers, and add one representative example with tuples as an extra case. (Tuple comparisons are harder to understand, so we should keep the simple cases.)

/// ```
///
/// The elements can be floats but no particular result is guaranteed
Expand All @@ -4105,6 +4105,26 @@ pub trait Itertools: Iterator {
///
/// The keys can be floats but no particular result is guaranteed
/// if a key is NaN.
///
/// # Examples
/// ```
/// use itertools::Itertools;
/// use itertools::MinMaxResult::{MinMax, NoElements, OneElement};
///
/// let cmp_key = |x: &&(i32, char)| x.0;
///
/// let a: [(i32, char); 0] = [];
/// assert_eq!(a.iter().minmax_by_key(cmp_key), NoElements);
///
/// let a = [(1, 'a')];
/// assert_eq!(a.iter().minmax_by_key(cmp_key), OneElement(&(1, 'a')));
///
/// let a = [(0, 'a'), (1, 'b')];
/// assert_eq!(a.iter().minmax_by_key(cmp_key), MinMax(&(0, 'a'), &(1, 'b')));
///
/// let a = [(1, 'a'), (1, 'b'), (1, 'c')];
/// assert_eq!(a.iter().minmax_by_key(cmp_key), MinMax(&(1, 'a'), &(1, 'c')));
/// ```
fn minmax_by_key<K, F>(self, key: F) -> MinMaxResult<Self::Item>
where
Self: Sized,
Expand All @@ -4122,6 +4142,27 @@ pub trait Itertools: Iterator {
/// For the minimum, the first minimal element is returned. For the maximum,
/// the last maximal element wins. This matches the behavior of the standard
/// [`Iterator::min`] and [`Iterator::max`] methods.
///
/// # Examples
///
/// ```
/// use itertools::Itertools;
/// use itertools::MinMaxResult::{MinMax, NoElements, OneElement};
///
/// let abs_cmp = |x: &&(i32, char), y: &&(i32, char)| x.0.cmp(&y.0);
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abs_cmp does not seem a reasonable name for the closure.

///
/// let a: [(i32, char); 0] = [];
/// assert_eq!(a.iter().minmax_by(abs_cmp), NoElements);
///
/// let a = [(1, 'a')];
/// assert_eq!(a.iter().minmax_by(abs_cmp), OneElement(&(1, 'a')));
///
/// let a = [(0, 'a'), (1, 'b')];
/// assert_eq!(a.iter().minmax_by(abs_cmp), MinMax(&(0, 'a'), &(1, 'b')));
///
/// let a = [(1, 'a'), (1, 'b'), (1, 'c')];
/// assert_eq!(a.iter().minmax_by(abs_cmp), MinMax(&(1, 'a'), &(1, 'c')));
/// ```
fn minmax_by<F>(self, mut compare: F) -> MinMaxResult<Self::Item>
where
Self: Sized,
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