| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/itertools-0.10.5/src/grouping_map.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>grouping_map.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../itertools/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../itertools/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| <span id="522">522</span> |
| <span id="523">523</span> |
| <span id="524">524</span> |
| <span id="525">525</span> |
| <span id="526">526</span> |
| <span id="527">527</span> |
| <span id="528">528</span> |
| <span id="529">529</span> |
| <span id="530">530</span> |
| <span id="531">531</span> |
| <span id="532">532</span> |
| <span id="533">533</span> |
| <span id="534">534</span> |
| <span id="535">535</span> |
| </pre><pre class="rust"><code><span class="attribute">#![cfg(feature = <span class="string">"use_std"</span>)] |
| |
| </span><span class="kw">use </span><span class="kw">crate</span>::MinMaxResult; |
| <span class="kw">use </span>std::collections::HashMap; |
| <span class="kw">use </span>std::cmp::Ordering; |
| <span class="kw">use </span>std::hash::Hash; |
| <span class="kw">use </span>std::iter::Iterator; |
| <span class="kw">use </span>std::ops::{Add, Mul}; |
| |
| <span class="doccomment">/// A wrapper to allow for an easy [`into_grouping_map_by`](crate::Itertools::into_grouping_map_by) |
| </span><span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">pub struct </span>MapForGrouping<I, F>(I, F); |
| |
| <span class="kw">impl</span><I, F> MapForGrouping<I, F> { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(iter: I, key_mapper: F) -> <span class="self">Self </span>{ |
| <span class="self">Self</span>(iter, key_mapper) |
| } |
| } |
| |
| <span class="kw">impl</span><K, V, I, F> Iterator <span class="kw">for </span>MapForGrouping<I, F> |
| <span class="kw">where </span>I: Iterator<Item = V>, |
| K: Hash + Eq, |
| F: FnMut(<span class="kw-2">&</span>V) -> K, |
| { |
| <span class="kw">type </span>Item = (K, V); |
| <span class="kw">fn </span>next(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>::Item> { |
| <span class="self">self</span>.<span class="number">0</span>.next().map(|val| ((<span class="self">self</span>.<span class="number">1</span>)(<span class="kw-2">&</span>val), val)) |
| } |
| } |
| |
| <span class="doccomment">/// Creates a new `GroupingMap` from `iter` |
| </span><span class="kw">pub fn </span>new<I, K, V>(iter: I) -> GroupingMap<I> |
| <span class="kw">where </span>I: Iterator<Item = (K, V)>, |
| K: Hash + Eq, |
| { |
| GroupingMap { iter } |
| } |
| |
| <span class="doccomment">/// `GroupingMapBy` is an intermediate struct for efficient group-and-fold operations. |
| /// |
| /// See [`GroupingMap`] for more informations. |
| </span><span class="kw">pub type </span>GroupingMapBy<I, F> = GroupingMap<MapForGrouping<I, F>>; |
| |
| <span class="doccomment">/// `GroupingMap` is an intermediate struct for efficient group-and-fold operations. |
| /// It groups elements by their key and at the same time fold each group |
| /// using some aggregating operation. |
| /// |
| /// No method on this struct performs temporary allocations. |
| </span><span class="attribute">#[derive(Clone, Debug)] |
| #[must_use = <span class="string">"GroupingMap is lazy and do nothing unless consumed"</span>] |
| </span><span class="kw">pub struct </span>GroupingMap<I> { |
| iter: I, |
| } |
| |
| <span class="kw">impl</span><I, K, V> GroupingMap<I> |
| <span class="kw">where </span>I: Iterator<Item = (K, V)>, |
| K: Hash + Eq, |
| { |
| <span class="doccomment">/// This is the generic way to perform any operation on a `GroupingMap`. |
| /// It's suggested to use this method only to implement custom operations |
| /// when the already provided ones are not enough. |
| /// |
| /// Groups elements from the `GroupingMap` source by key and applies `operation` to the elements |
| /// of each group sequentially, passing the previously accumulated value, a reference to the key |
| /// and the current element as arguments, and stores the results in an `HashMap`. |
| /// |
| /// The `operation` function is invoked on each element with the following parameters: |
| /// - the current value of the accumulator of the group if there is currently one; |
| /// - a reference to the key of the group this element belongs to; |
| /// - the element from the source being aggregated; |
| /// |
| /// If `operation` returns `Some(element)` then the accumulator is updated with `element`, |
| /// otherwise the previous accumulation is discarded. |
| /// |
| /// Return a `HashMap` associating the key of each group with the result of aggregation of |
| /// that group's elements. If the aggregation of the last element of a group discards the |
| /// accumulator then there won't be an entry associated to that group's key. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let data = vec![2, 8, 5, 7, 9, 0, 4, 10]; |
| /// let lookup = data.into_iter() |
| /// .into_grouping_map_by(|&n| n % 4) |
| /// .aggregate(|acc, _key, val| { |
| /// if val == 0 || val == 10 { |
| /// None |
| /// } else { |
| /// Some(acc.unwrap_or(0) + val) |
| /// } |
| /// }); |
| /// |
| /// assert_eq!(lookup[&0], 4); // 0 resets the accumulator so only 4 is summed |
| /// assert_eq!(lookup[&1], 5 + 9); |
| /// assert_eq!(lookup.get(&2), None); // 10 resets the accumulator and nothing is summed afterward |
| /// assert_eq!(lookup[&3], 7); |
| /// assert_eq!(lookup.len(), 3); // The final keys are only 0, 1 and 2 |
| /// ``` |
| </span><span class="kw">pub fn </span>aggregate<FO, R>(<span class="self">self</span>, <span class="kw-2">mut </span>operation: FO) -> HashMap<K, R> |
| <span class="kw">where </span>FO: FnMut(<span class="prelude-ty">Option</span><R>, <span class="kw-2">&</span>K, V) -> <span class="prelude-ty">Option</span><R>, |
| { |
| <span class="kw">let </span><span class="kw-2">mut </span>destination_map = HashMap::new(); |
| |
| <span class="self">self</span>.iter.for_each(|(key, val)| { |
| <span class="kw">let </span>acc = destination_map.remove(<span class="kw-2">&</span>key); |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(op_res) = operation(acc, <span class="kw-2">&</span>key, val) { |
| destination_map.insert(key, op_res); |
| } |
| }); |
| |
| destination_map |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and applies `operation` to the elements |
| /// of each group sequentially, passing the previously accumulated value, a reference to the key |
| /// and the current element as arguments, and stores the results in a new map. |
| /// |
| /// `init` is the value from which will be cloned the initial value of each accumulator. |
| /// |
| /// `operation` is a function that is invoked on each element with the following parameters: |
| /// - the current value of the accumulator of the group; |
| /// - a reference to the key of the group this element belongs to; |
| /// - the element from the source being accumulated. |
| /// |
| /// Return a `HashMap` associating the key of each group with the result of folding that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = (1..=7) |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .fold(0, |acc, _key, val| acc + val); |
| /// |
| /// assert_eq!(lookup[&0], 3 + 6); |
| /// assert_eq!(lookup[&1], 1 + 4 + 7); |
| /// assert_eq!(lookup[&2], 2 + 5); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>fold<FO, R>(<span class="self">self</span>, init: R, <span class="kw-2">mut </span>operation: FO) -> HashMap<K, R> |
| <span class="kw">where </span>R: Clone, |
| FO: FnMut(R, <span class="kw-2">&</span>K, V) -> R, |
| { |
| <span class="self">self</span>.aggregate(|acc, key, val| { |
| <span class="kw">let </span>acc = acc.unwrap_or_else(|| init.clone()); |
| <span class="prelude-val">Some</span>(operation(acc, key, val)) |
| }) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and applies `operation` to the elements |
| /// of each group sequentially, passing the previously accumulated value, a reference to the key |
| /// and the current element as arguments, and stores the results in a new map. |
| /// |
| /// This is similar to [`fold`] but the initial value of the accumulator is the first element of the group. |
| /// |
| /// `operation` is a function that is invoked on each element with the following parameters: |
| /// - the current value of the accumulator of the group; |
| /// - a reference to the key of the group this element belongs to; |
| /// - the element from the source being accumulated. |
| /// |
| /// Return a `HashMap` associating the key of each group with the result of folding that group's elements. |
| /// |
| /// [`fold`]: GroupingMap::fold |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = (1..=7) |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .fold_first(|acc, _key, val| acc + val); |
| /// |
| /// assert_eq!(lookup[&0], 3 + 6); |
| /// assert_eq!(lookup[&1], 1 + 4 + 7); |
| /// assert_eq!(lookup[&2], 2 + 5); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>fold_first<FO>(<span class="self">self</span>, <span class="kw-2">mut </span>operation: FO) -> HashMap<K, V> |
| <span class="kw">where </span>FO: FnMut(V, <span class="kw-2">&</span>K, V) -> V, |
| { |
| <span class="self">self</span>.aggregate(|acc, key, val| { |
| <span class="prelude-val">Some</span>(<span class="kw">match </span>acc { |
| <span class="prelude-val">Some</span>(acc) => operation(acc, key, val), |
| <span class="prelude-val">None </span>=> val, |
| }) |
| }) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and collects the elements of each group in |
| /// an instance of `C`. The iteration order is preserved when inserting elements. |
| /// |
| /// Return a `HashMap` associating the key of each group with the collection containing that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// use std::collections::HashSet; |
| /// |
| /// let lookup = vec![0, 1, 2, 3, 4, 5, 6, 2, 3, 6].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .collect::<HashSet<_>>(); |
| /// |
| /// assert_eq!(lookup[&0], vec![0, 3, 6].into_iter().collect::<HashSet<_>>()); |
| /// assert_eq!(lookup[&1], vec![1, 4].into_iter().collect::<HashSet<_>>()); |
| /// assert_eq!(lookup[&2], vec![2, 5].into_iter().collect::<HashSet<_>>()); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>collect<C>(<span class="self">self</span>) -> HashMap<K, C> |
| <span class="kw">where </span>C: Default + Extend<V>, |
| { |
| <span class="kw">let </span><span class="kw-2">mut </span>destination_map = HashMap::new(); |
| |
| <span class="self">self</span>.iter.for_each(|(key, val)| { |
| destination_map.entry(key).or_insert_with(C::default).extend(<span class="prelude-val">Some</span>(val)); |
| }); |
| |
| destination_map |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and finds the maximum of each group. |
| /// |
| /// If several elements are equally maximum, the last element is picked. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the maximum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .max(); |
| /// |
| /// assert_eq!(lookup[&0], 12); |
| /// assert_eq!(lookup[&1], 7); |
| /// assert_eq!(lookup[&2], 8); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>max(<span class="self">self</span>) -> HashMap<K, V> |
| <span class="kw">where </span>V: Ord, |
| { |
| <span class="self">self</span>.max_by(|<span class="kw">_</span>, v1, v2| V::cmp(v1, v2)) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and finds the maximum of each group |
| /// with respect to the specified comparison function. |
| /// |
| /// If several elements are equally maximum, the last element is picked. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the maximum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .max_by(|_key, x, y| y.cmp(x)); |
| /// |
| /// assert_eq!(lookup[&0], 3); |
| /// assert_eq!(lookup[&1], 1); |
| /// assert_eq!(lookup[&2], 5); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>max_by<F>(<span class="self">self</span>, <span class="kw-2">mut </span>compare: F) -> HashMap<K, V> |
| <span class="kw">where </span>F: FnMut(<span class="kw-2">&</span>K, <span class="kw-2">&</span>V, <span class="kw-2">&</span>V) -> Ordering, |
| { |
| <span class="self">self</span>.fold_first(|acc, key, val| <span class="kw">match </span>compare(key, <span class="kw-2">&</span>acc, <span class="kw-2">&</span>val) { |
| Ordering::Less | Ordering::Equal => val, |
| Ordering::Greater => acc |
| }) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and finds the element of each group |
| /// that gives the maximum from the specified function. |
| /// |
| /// If several elements are equally maximum, the last element is picked. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the maximum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .max_by_key(|_key, &val| val % 4); |
| /// |
| /// assert_eq!(lookup[&0], 3); |
| /// assert_eq!(lookup[&1], 7); |
| /// assert_eq!(lookup[&2], 5); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>max_by_key<F, CK>(<span class="self">self</span>, <span class="kw-2">mut </span>f: F) -> HashMap<K, V> |
| <span class="kw">where </span>F: FnMut(<span class="kw-2">&</span>K, <span class="kw-2">&</span>V) -> CK, |
| CK: Ord, |
| { |
| <span class="self">self</span>.max_by(|key, v1, v2| f(key, v1).cmp(<span class="kw-2">&</span>f(key, v2))) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and finds the minimum of each group. |
| /// |
| /// If several elements are equally minimum, the first element is picked. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the minimum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .min(); |
| /// |
| /// assert_eq!(lookup[&0], 3); |
| /// assert_eq!(lookup[&1], 1); |
| /// assert_eq!(lookup[&2], 5); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>min(<span class="self">self</span>) -> HashMap<K, V> |
| <span class="kw">where </span>V: Ord, |
| { |
| <span class="self">self</span>.min_by(|<span class="kw">_</span>, v1, v2| V::cmp(v1, v2)) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and finds the minimum of each group |
| /// with respect to the specified comparison function. |
| /// |
| /// If several elements are equally minimum, the first element is picked. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the minimum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .min_by(|_key, x, y| y.cmp(x)); |
| /// |
| /// assert_eq!(lookup[&0], 12); |
| /// assert_eq!(lookup[&1], 7); |
| /// assert_eq!(lookup[&2], 8); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>min_by<F>(<span class="self">self</span>, <span class="kw-2">mut </span>compare: F) -> HashMap<K, V> |
| <span class="kw">where </span>F: FnMut(<span class="kw-2">&</span>K, <span class="kw-2">&</span>V, <span class="kw-2">&</span>V) -> Ordering, |
| { |
| <span class="self">self</span>.fold_first(|acc, key, val| <span class="kw">match </span>compare(key, <span class="kw-2">&</span>acc, <span class="kw-2">&</span>val) { |
| Ordering::Less | Ordering::Equal => acc, |
| Ordering::Greater => val |
| }) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and finds the element of each group |
| /// that gives the minimum from the specified function. |
| /// |
| /// If several elements are equally minimum, the first element is picked. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the minimum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .min_by_key(|_key, &val| val % 4); |
| /// |
| /// assert_eq!(lookup[&0], 12); |
| /// assert_eq!(lookup[&1], 4); |
| /// assert_eq!(lookup[&2], 8); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>min_by_key<F, CK>(<span class="self">self</span>, <span class="kw-2">mut </span>f: F) -> HashMap<K, V> |
| <span class="kw">where </span>F: FnMut(<span class="kw-2">&</span>K, <span class="kw-2">&</span>V) -> CK, |
| CK: Ord, |
| { |
| <span class="self">self</span>.min_by(|key, v1, v2| f(key, v1).cmp(<span class="kw-2">&</span>f(key, v2))) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and find the maximum and minimum of |
| /// each group. |
| /// |
| /// If several elements are equally maximum, the last element is picked. |
| /// If several elements are equally minimum, the first element is picked. |
| /// |
| /// See [.minmax()](crate::Itertools::minmax) for the non-grouping version. |
| /// |
| /// Differences from the non grouping version: |
| /// - It never produces a `MinMaxResult::NoElements` |
| /// - It doesn't have any speedup |
| /// |
| /// Returns a `HashMap` associating the key of each group with the minimum and maximum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// use itertools::MinMaxResult::{OneElement, MinMax}; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .minmax(); |
| /// |
| /// assert_eq!(lookup[&0], MinMax(3, 12)); |
| /// assert_eq!(lookup[&1], MinMax(1, 7)); |
| /// assert_eq!(lookup[&2], OneElement(5)); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>minmax(<span class="self">self</span>) -> HashMap<K, MinMaxResult<V>> |
| <span class="kw">where </span>V: Ord, |
| { |
| <span class="self">self</span>.minmax_by(|<span class="kw">_</span>, v1, v2| V::cmp(v1, v2)) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and find the maximum and minimum of |
| /// each group with respect to the specified comparison function. |
| /// |
| /// If several elements are equally maximum, the last element is picked. |
| /// If several elements are equally minimum, the first element is picked. |
| /// |
| /// It has the same differences from the non-grouping version as `minmax`. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the minimum and maximum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// use itertools::MinMaxResult::{OneElement, MinMax}; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .minmax_by(|_key, x, y| y.cmp(x)); |
| /// |
| /// assert_eq!(lookup[&0], MinMax(12, 3)); |
| /// assert_eq!(lookup[&1], MinMax(7, 1)); |
| /// assert_eq!(lookup[&2], OneElement(5)); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>minmax_by<F>(<span class="self">self</span>, <span class="kw-2">mut </span>compare: F) -> HashMap<K, MinMaxResult<V>> |
| <span class="kw">where </span>F: FnMut(<span class="kw-2">&</span>K, <span class="kw-2">&</span>V, <span class="kw-2">&</span>V) -> Ordering, |
| { |
| <span class="self">self</span>.aggregate(|acc, key, val| { |
| <span class="prelude-val">Some</span>(<span class="kw">match </span>acc { |
| <span class="prelude-val">Some</span>(MinMaxResult::OneElement(e)) => { |
| <span class="kw">if </span>compare(key, <span class="kw-2">&</span>val, <span class="kw-2">&</span>e) == Ordering::Less { |
| MinMaxResult::MinMax(val, e) |
| } <span class="kw">else </span>{ |
| MinMaxResult::MinMax(e, val) |
| } |
| } |
| <span class="prelude-val">Some</span>(MinMaxResult::MinMax(min, max)) => { |
| <span class="kw">if </span>compare(key, <span class="kw-2">&</span>val, <span class="kw-2">&</span>min) == Ordering::Less { |
| MinMaxResult::MinMax(val, max) |
| } <span class="kw">else if </span>compare(key, <span class="kw-2">&</span>val, <span class="kw-2">&</span>max) != Ordering::Less { |
| MinMaxResult::MinMax(min, val) |
| } <span class="kw">else </span>{ |
| MinMaxResult::MinMax(min, max) |
| } |
| } |
| <span class="prelude-val">None </span>=> MinMaxResult::OneElement(val), |
| <span class="prelude-val">Some</span>(MinMaxResult::NoElements) => <span class="macro">unreachable!</span>(), |
| }) |
| }) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and find the elements of each group |
| /// that gives the minimum and maximum from the specified function. |
| /// |
| /// If several elements are equally maximum, the last element is picked. |
| /// If several elements are equally minimum, the first element is picked. |
| /// |
| /// It has the same differences from the non-grouping version as `minmax`. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the minimum and maximum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// use itertools::MinMaxResult::{OneElement, MinMax}; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .minmax_by_key(|_key, &val| val % 4); |
| /// |
| /// assert_eq!(lookup[&0], MinMax(12, 3)); |
| /// assert_eq!(lookup[&1], MinMax(4, 7)); |
| /// assert_eq!(lookup[&2], OneElement(5)); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>minmax_by_key<F, CK>(<span class="self">self</span>, <span class="kw-2">mut </span>f: F) -> HashMap<K, MinMaxResult<V>> |
| <span class="kw">where </span>F: FnMut(<span class="kw-2">&</span>K, <span class="kw-2">&</span>V) -> CK, |
| CK: Ord, |
| { |
| <span class="self">self</span>.minmax_by(|key, v1, v2| f(key, v1).cmp(<span class="kw-2">&</span>f(key, v2))) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and sums them. |
| /// |
| /// This is just a shorthand for `self.fold_first(|acc, _, val| acc + val)`. |
| /// It is more limited than `Iterator::sum` since it doesn't use the `Sum` trait. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the sum of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .sum(); |
| /// |
| /// assert_eq!(lookup[&0], 3 + 9 + 12); |
| /// assert_eq!(lookup[&1], 1 + 4 + 7); |
| /// assert_eq!(lookup[&2], 5 + 8); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>sum(<span class="self">self</span>) -> HashMap<K, V> |
| <span class="kw">where </span>V: Add<V, Output = V> |
| { |
| <span class="self">self</span>.fold_first(|acc, <span class="kw">_</span>, val| acc + val) |
| } |
| |
| <span class="doccomment">/// Groups elements from the `GroupingMap` source by key and multiply them. |
| /// |
| /// This is just a shorthand for `self.fold_first(|acc, _, val| acc * val)`. |
| /// It is more limited than `Iterator::product` since it doesn't use the `Product` trait. |
| /// |
| /// Returns a `HashMap` associating the key of each group with the product of that group's elements. |
| /// |
| /// ``` |
| /// use itertools::Itertools; |
| /// |
| /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter() |
| /// .into_grouping_map_by(|&n| n % 3) |
| /// .product(); |
| /// |
| /// assert_eq!(lookup[&0], 3 * 9 * 12); |
| /// assert_eq!(lookup[&1], 1 * 4 * 7); |
| /// assert_eq!(lookup[&2], 5 * 8); |
| /// assert_eq!(lookup.len(), 3); |
| /// ``` |
| </span><span class="kw">pub fn </span>product(<span class="self">self</span>) -> HashMap<K, V> |
| <span class="kw">where </span>V: Mul<V, Output = V>, |
| { |
| <span class="self">self</span>.fold_first(|acc, <span class="kw">_</span>, val| acc * val) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="itertools" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
