diff --git a/src/extrema_set.rs b/src/extrema_set.rs new file mode 100644 index 000000000..ae128364c --- /dev/null +++ b/src/extrema_set.rs @@ -0,0 +1,48 @@ +use std::cmp::Ordering; + +/// Implementation guts for `min_set`, `min_set_by`, and `min_set_by_key`. +pub fn min_set_impl( + mut it: I, + mut key_for: F, + mut compare: Compare, +) -> Vec +where + I: Iterator, + F: FnMut(&I::Item) -> K, + Compare: FnMut(&I::Item, &I::Item, &K, &K) -> Ordering, +{ + match it.next() { + None => Vec::new(), + Some(element) => { + let mut current_key = key_for(&element); + let mut result = vec![element]; + it.for_each(|element| { + let key = key_for(&element); + match compare(&element, &result[0], &key, ¤t_key) { + Ordering::Less => { + result.clear(); + result.push(element); + current_key = key; + } + Ordering::Equal => { + result.push(element); + } + Ordering::Greater => {} + } + }); + result + } + } +} + +/// Implementation guts for `ax_set`, `max_set_by`, and `max_set_by_key`. +pub fn max_set_impl(it: I, key_for: F, mut compare: Compare) -> Vec +where + I: Iterator, + F: FnMut(&I::Item) -> K, + Compare: FnMut(&I::Item, &I::Item, &K, &K) -> Ordering, +{ + min_set_impl(it, key_for, |it1, it2, key1, key2| { + compare(it2, it1, key2, key1) + }) +} diff --git a/src/lib.rs b/src/lib.rs index f2ecd3ec7..c2c1750be 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -197,6 +197,8 @@ mod combinations_with_replacement; mod exactly_one_err; mod diff; mod flatten_ok; +#[cfg(feature = "use_std")] +mod extrema_set; mod format; #[cfg(feature = "use_std")] mod grouping_map; @@ -2902,6 +2904,194 @@ pub trait Itertools : Iterator { grouping_map::new(grouping_map::MapForGrouping::new(self, key_mapper)) } + /// Return all minimum elements of an iterator. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().min_set(), Vec::<&i32>::new()); + /// + /// let a = [1]; + /// assert_eq!(a.iter().min_set(), vec![&1]); + /// + /// let a = [1, 2, 3, 4, 5]; + /// assert_eq!(a.iter().min_set(), vec![&1]); + /// + /// let a = [1, 1, 1, 1]; + /// assert_eq!(a.iter().min_set(), vec![&1, &1, &1, &1]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn min_set(self) -> Vec + where Self: Sized, Self::Item: Ord + { + extrema_set::min_set_impl(self, |_| (), |x, y, _, _| x.cmp(y)) + } + + /// Return all minimum elements of an iterator, as determined by + /// the specified function. + /// + /// # Examples + /// + /// ``` + /// # use std::cmp::Ordering; + /// use itertools::Itertools; + /// + /// let a: [(i32, i32); 0] = []; + /// assert_eq!(a.iter().min_set_by(|_, _| Ordering::Equal), Vec::<&(i32, i32)>::new()); + /// + /// let a = [(1, 2)]; + /// assert_eq!(a.iter().min_set_by(|&&(k1,_), &&(k2, _)| k1.cmp(&k2)), vec![&(1, 2)]); + /// + /// let a = [(1, 2), (2, 2), (3, 9), (4, 8), (5, 9)]; + /// assert_eq!(a.iter().min_set_by(|&&(_,k1), &&(_,k2)| k1.cmp(&k2)), vec![&(1, 2), &(2, 2)]); + /// + /// let a = [(1, 2), (1, 3), (1, 4), (1, 5)]; + /// assert_eq!(a.iter().min_set_by(|&&(k1,_), &&(k2, _)| k1.cmp(&k2)), vec![&(1, 2), &(1, 3), &(1, 4), &(1, 5)]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn min_set_by(self, mut compare: F) -> Vec + where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering + { + extrema_set::min_set_impl( + self, + |_| (), + |x, y, _, _| compare(x, y) + ) + } + + /// Return all minimum elements of an iterator, as determined by + /// the specified function. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [(i32, i32); 0] = []; + /// assert_eq!(a.iter().min_set_by_key(|_| ()), Vec::<&(i32, i32)>::new()); + /// + /// let a = [(1, 2)]; + /// assert_eq!(a.iter().min_set_by_key(|&&(k,_)| k), vec![&(1, 2)]); + /// + /// let a = [(1, 2), (2, 2), (3, 9), (4, 8), (5, 9)]; + /// assert_eq!(a.iter().min_set_by_key(|&&(_, k)| k), vec![&(1, 2), &(2, 2)]); + /// + /// let a = [(1, 2), (1, 3), (1, 4), (1, 5)]; + /// assert_eq!(a.iter().min_set_by_key(|&&(k, _)| k), vec![&(1, 2), &(1, 3), &(1, 4), &(1, 5)]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn min_set_by_key(self, key: F) -> Vec + where Self: Sized, K: Ord, F: FnMut(&Self::Item) -> K + { + extrema_set::min_set_impl(self, key, |_, _, kx, ky| kx.cmp(ky)) + } + + /// Return all maximum elements of an iterator. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [i32; 0] = []; + /// assert_eq!(a.iter().max_set(), Vec::<&i32>::new()); + /// + /// let a = [1]; + /// assert_eq!(a.iter().max_set(), vec![&1]); + /// + /// let a = [1, 2, 3, 4, 5]; + /// assert_eq!(a.iter().max_set(), vec![&5]); + /// + /// let a = [1, 1, 1, 1]; + /// assert_eq!(a.iter().max_set(), vec![&1, &1, &1, &1]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn max_set(self) -> Vec + where Self: Sized, Self::Item: Ord + { + extrema_set::max_set_impl(self, |_| (), |x, y, _, _| x.cmp(y)) + } + + /// Return all maximum elements of an iterator, as determined by + /// the specified function. + /// + /// # Examples + /// + /// ``` + /// # use std::cmp::Ordering; + /// use itertools::Itertools; + /// + /// let a: [(i32, i32); 0] = []; + /// assert_eq!(a.iter().max_set_by(|_, _| Ordering::Equal), Vec::<&(i32, i32)>::new()); + /// + /// let a = [(1, 2)]; + /// assert_eq!(a.iter().max_set_by(|&&(k1,_), &&(k2, _)| k1.cmp(&k2)), vec![&(1, 2)]); + /// + /// let a = [(1, 2), (2, 2), (3, 9), (4, 8), (5, 9)]; + /// assert_eq!(a.iter().max_set_by(|&&(_,k1), &&(_,k2)| k1.cmp(&k2)), vec![&(3, 9), &(5, 9)]); + /// + /// let a = [(1, 2), (1, 3), (1, 4), (1, 5)]; + /// assert_eq!(a.iter().max_set_by(|&&(k1,_), &&(k2, _)| k1.cmp(&k2)), vec![&(1, 2), &(1, 3), &(1, 4), &(1, 5)]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn max_set_by(self, mut compare: F) -> Vec + where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering + { + extrema_set::max_set_impl( + self, + |_| (), + |x, y, _, _| compare(x, y) + ) + } + + /// Return all minimum elements of an iterator, as determined by + /// the specified function. + /// + /// # Examples + /// + /// ``` + /// use itertools::Itertools; + /// + /// let a: [(i32, i32); 0] = []; + /// assert_eq!(a.iter().max_set_by_key(|_| ()), Vec::<&(i32, i32)>::new()); + /// + /// let a = [(1, 2)]; + /// assert_eq!(a.iter().max_set_by_key(|&&(k,_)| k), vec![&(1, 2)]); + /// + /// let a = [(1, 2), (2, 2), (3, 9), (4, 8), (5, 9)]; + /// assert_eq!(a.iter().max_set_by_key(|&&(_, k)| k), vec![&(3, 9), &(5, 9)]); + /// + /// let a = [(1, 2), (1, 3), (1, 4), (1, 5)]; + /// assert_eq!(a.iter().max_set_by_key(|&&(k, _)| k), vec![&(1, 2), &(1, 3), &(1, 4), &(1, 5)]); + /// ``` + /// + /// The elements can be floats but no particular result is guaranteed + /// if an element is NaN. + #[cfg(feature = "use_std")] + fn max_set_by_key(self, key: F) -> Vec + where Self: Sized, K: Ord, F: FnMut(&Self::Item) -> K + { + extrema_set::max_set_impl(self, key, |_, _, kx, ky| kx.cmp(ky)) + } + /// Return the minimum and maximum elements in the iterator. /// /// The return type `MinMaxResult` is an enum of three variants: diff --git a/tests/quick.rs b/tests/quick.rs index 7e222a641..5829d1c1d 100644 --- a/tests/quick.rs +++ b/tests/quick.rs @@ -1693,3 +1693,62 @@ quickcheck! { } } +quickcheck! { + fn min_set_contains_min(a: Vec<(usize, char)>) -> bool { + let result_set = a.iter().min_set(); + if let Some(result_element) = a.iter().min() { + result_set.contains(&result_element) + } else { + result_set.is_empty() + } + } + + fn min_set_by_contains_min(a: Vec<(usize, char)>) -> bool { + let compare = |x: &&(usize, char), y: &&(usize, char)| x.1.cmp(&y.1); + let result_set = a.iter().min_set_by(compare); + if let Some(result_element) = a.iter().min_by(compare) { + result_set.contains(&result_element) + } else { + result_set.is_empty() + } + } + + fn min_set_by_key_contains_min(a: Vec<(usize, char)>) -> bool { + let key = |x: &&(usize, char)| x.1; + let result_set = a.iter().min_set_by_key(&key); + if let Some(result_element) = a.iter().min_by_key(&key) { + result_set.contains(&result_element) + } else { + result_set.is_empty() + } + } + + fn max_set_contains_max(a: Vec<(usize, char)>) -> bool { + let result_set = a.iter().max_set(); + if let Some(result_element) = a.iter().max() { + result_set.contains(&result_element) + } else { + result_set.is_empty() + } + } + + fn max_set_by_contains_max(a: Vec<(usize, char)>) -> bool { + let compare = |x: &&(usize, char), y: &&(usize, char)| x.1.cmp(&y.1); + let result_set = a.iter().max_set_by(compare); + if let Some(result_element) = a.iter().max_by(compare) { + result_set.contains(&result_element) + } else { + result_set.is_empty() + } + } + + fn max_set_by_key_contains_max(a: Vec<(usize, char)>) -> bool { + let key = |x: &&(usize, char)| x.1; + let result_set = a.iter().max_set_by_key(&key); + if let Some(result_element) = a.iter().max_by_key(&key) { + result_set.contains(&result_element) + } else { + result_set.is_empty() + } + } +} diff --git a/tests/test_std.rs b/tests/test_std.rs index 2049d1597..4463d912f 100644 --- a/tests/test_std.rs +++ b/tests/test_std.rs @@ -992,6 +992,54 @@ fn diff_shorter() { }); } +#[test] +fn extrema_set() { + use std::cmp::Ordering; + + // A peculiar type: Equality compares both tuple items, but ordering only the + // first item. Used to distinguish equal elements. + #[derive(Clone, Debug, PartialEq, Eq)] + struct Val(u32, u32); + + impl PartialOrd for Val { + fn partial_cmp(&self, other: &Val) -> Option { + self.0.partial_cmp(&other.0) + } + } + + impl Ord for Val { + fn cmp(&self, other: &Val) -> Ordering { + self.0.cmp(&other.0) + } + } + + assert_eq!(None::.iter().min_set(), Vec::<&u32>::new()); + assert_eq!(None::.iter().max_set(), Vec::<&u32>::new()); + + assert_eq!(Some(1u32).iter().min_set(), vec![&1]); + assert_eq!(Some(1u32).iter().max_set(), vec![&1]); + + let data = vec![Val(0, 1), Val(2, 0), Val(0, 2), Val(1, 0), Val(2, 1)]; + + let min_set = data.iter().min_set(); + assert_eq!(min_set, vec![&Val(0, 1), &Val(0, 2)]); + + let min_set_by_key = data.iter().min_set_by_key(|v| v.1); + assert_eq!(min_set_by_key, vec![&Val(2, 0), &Val(1, 0)]); + + let min_set_by = data.iter().min_set_by(|x, y| x.1.cmp(&y.1)); + assert_eq!(min_set_by, vec![&Val(2, 0), &Val(1, 0)]); + + let max_set = data.iter().max_set(); + assert_eq!(max_set, vec![&Val(2, 0), &Val(2, 1)]); + + let max_set_by_key = data.iter().max_set_by_key(|v| v.1); + assert_eq!(max_set_by_key, vec![&Val(0, 2)]); + + let max_set_by = data.iter().max_set_by(|x, y| x.1.cmp(&y.1)); + assert_eq!(max_set_by, vec![&Val(0, 2)]); +} + #[test] fn minmax() { use std::cmp::Ordering; @@ -1119,4 +1167,4 @@ fn multiunzip() { let (): () = [(), (), ()].iter().cloned().multiunzip(); let t: (Vec<_>, Vec<_>, Vec<_>, Vec<_>, Vec<_>, Vec<_>, Vec<_>, Vec<_>, Vec<_>, Vec<_>, Vec<_>, Vec<_>) = [(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11)].iter().cloned().multiunzip(); assert_eq!(t, (vec![0], vec![1], vec![2], vec![3], vec![4], vec![5], vec![6], vec![7], vec![8], vec![9], vec![10], vec![11])); -} \ No newline at end of file +}