Source code
Revision control
Copy as Markdown
Other Tools
//! Licensed under the Apache License, Version 2.0
//! option. This file may not be copied, modified, or distributed
//! except according to those terms.
mod coalesce;
mod map;
mod multi_product;
pub use self::coalesce::*;
pub use self::map::{map_into, map_ok, MapInto, MapOk};
#[allow(deprecated)]
pub use self::map::MapResults;
#[cfg(feature = "use_alloc")]
pub use self::multi_product::*;
use std::fmt;
use std::iter::{Fuse, Peekable, FromIterator, FusedIterator};
use std::marker::PhantomData;
use crate::size_hint;
/// An iterator adaptor that alternates elements from two iterators until both
/// run out.
///
/// This iterator is *fused*.
///
/// See [`.interleave()`](crate::Itertools::interleave) for more information.
#[derive(Clone, Debug)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Interleave<I, J> {
a: Fuse<I>,
b: Fuse<J>,
flag: bool,
}
/// Create an iterator that interleaves elements in `i` and `j`.
///
/// [`IntoIterator`] enabled version of `[Itertools::interleave]`.
pub fn interleave<I, J>(i: I, j: J) -> Interleave<<I as IntoIterator>::IntoIter, <J as IntoIterator>::IntoIter>
where I: IntoIterator,
J: IntoIterator<Item = I::Item>
{
Interleave {
a: i.into_iter().fuse(),
b: j.into_iter().fuse(),
flag: false,
}
}
impl<I, J> Iterator for Interleave<I, J>
where I: Iterator,
J: Iterator<Item = I::Item>
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
self.flag = !self.flag;
if self.flag {
match self.a.next() {
None => self.b.next(),
r => r,
}
} else {
match self.b.next() {
None => self.a.next(),
r => r,
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
size_hint::add(self.a.size_hint(), self.b.size_hint())
}
}
impl<I, J> FusedIterator for Interleave<I, J>
where I: Iterator,
J: Iterator<Item = I::Item>
{}
/// An iterator adaptor that alternates elements from the two iterators until
/// one of them runs out.
///
/// This iterator is *fused*.
///
/// See [`.interleave_shortest()`](crate::Itertools::interleave_shortest)
/// for more information.
#[derive(Clone, Debug)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct InterleaveShortest<I, J>
where I: Iterator,
J: Iterator<Item = I::Item>
{
it0: I,
it1: J,
phase: bool, // false ==> it0, true ==> it1
}
/// Create a new `InterleaveShortest` iterator.
pub fn interleave_shortest<I, J>(a: I, b: J) -> InterleaveShortest<I, J>
where I: Iterator,
J: Iterator<Item = I::Item>
{
InterleaveShortest {
it0: a,
it1: b,
phase: false,
}
}
impl<I, J> Iterator for InterleaveShortest<I, J>
where I: Iterator,
J: Iterator<Item = I::Item>
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
let e = if self.phase { self.it1.next() } else { self.it0.next() };
if e.is_some() {
self.phase = !self.phase;
}
e
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (curr_hint, next_hint) = {
let it0_hint = self.it0.size_hint();
let it1_hint = self.it1.size_hint();
if self.phase {
(it1_hint, it0_hint)
} else {
(it0_hint, it1_hint)
}
};
let (curr_lower, curr_upper) = curr_hint;
let (next_lower, next_upper) = next_hint;
let (combined_lower, combined_upper) =
size_hint::mul_scalar(size_hint::min(curr_hint, next_hint), 2);
let lower =
if curr_lower > next_lower {
combined_lower + 1
} else {
combined_lower
};
let upper = {
let extra_elem = match (curr_upper, next_upper) {
(_, None) => false,
(None, Some(_)) => true,
(Some(curr_max), Some(next_max)) => curr_max > next_max,
};
if extra_elem {
combined_upper.and_then(|x| x.checked_add(1))
} else {
combined_upper
}
};
(lower, upper)
}
}
impl<I, J> FusedIterator for InterleaveShortest<I, J>
where I: FusedIterator,
J: FusedIterator<Item = I::Item>
{}
#[derive(Clone, Debug)]
/// An iterator adaptor that allows putting back a single
/// item to the front of the iterator.
///
/// Iterator element type is `I::Item`.
pub struct PutBack<I>
where I: Iterator
{
top: Option<I::Item>,
iter: I,
}
/// Create an iterator where you can put back a single item
pub fn put_back<I>(iterable: I) -> PutBack<I::IntoIter>
where I: IntoIterator
{
PutBack {
top: None,
iter: iterable.into_iter(),
}
}
impl<I> PutBack<I>
where I: Iterator
{
/// put back value `value` (builder method)
pub fn with_value(mut self, value: I::Item) -> Self {
self.put_back(value);
self
}
/// Split the `PutBack` into its parts.
#[inline]
pub fn into_parts(self) -> (Option<I::Item>, I) {
let PutBack{top, iter} = self;
(top, iter)
}
/// Put back a single value to the front of the iterator.
///
/// If a value is already in the put back slot, it is overwritten.
#[inline]
pub fn put_back(&mut self, x: I::Item) {
self.top = Some(x);
}
}
impl<I> Iterator for PutBack<I>
where I: Iterator
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
match self.top {
None => self.iter.next(),
ref mut some => some.take(),
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
// Not ExactSizeIterator because size may be larger than usize
size_hint::add_scalar(self.iter.size_hint(), self.top.is_some() as usize)
}
fn count(self) -> usize {
self.iter.count() + (self.top.is_some() as usize)
}
fn last(self) -> Option<Self::Item> {
self.iter.last().or(self.top)
}
fn nth(&mut self, n: usize) -> Option<Self::Item> {
match self.top {
None => self.iter.nth(n),
ref mut some => {
if n == 0 {
some.take()
} else {
*some = None;
self.iter.nth(n - 1)
}
}
}
}
fn all<G>(&mut self, mut f: G) -> bool
where G: FnMut(Self::Item) -> bool
{
if let Some(elt) = self.top.take() {
if !f(elt) {
return false;
}
}
self.iter.all(f)
}
fn fold<Acc, G>(mut self, init: Acc, mut f: G) -> Acc
where G: FnMut(Acc, Self::Item) -> Acc,
{
let mut accum = init;
if let Some(elt) = self.top.take() {
accum = f(accum, elt);
}
self.iter.fold(accum, f)
}
}
#[derive(Debug, Clone)]
/// An iterator adaptor that iterates over the cartesian product of
/// the element sets of two iterators `I` and `J`.
///
/// Iterator element type is `(I::Item, J::Item)`.
///
/// See [`.cartesian_product()`](crate::Itertools::cartesian_product) for more information.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Product<I, J>
where I: Iterator
{
a: I,
a_cur: Option<I::Item>,
b: J,
b_orig: J,
}
/// Create a new cartesian product iterator
///
/// Iterator element type is `(I::Item, J::Item)`.
pub fn cartesian_product<I, J>(mut i: I, j: J) -> Product<I, J>
where I: Iterator,
J: Clone + Iterator,
I::Item: Clone
{
Product {
a_cur: i.next(),
a: i,
b: j.clone(),
b_orig: j,
}
}
impl<I, J> Iterator for Product<I, J>
where I: Iterator,
J: Clone + Iterator,
I::Item: Clone
{
type Item = (I::Item, J::Item);
fn next(&mut self) -> Option<Self::Item> {
let elt_b = match self.b.next() {
None => {
self.b = self.b_orig.clone();
match self.b.next() {
None => return None,
Some(x) => {
self.a_cur = self.a.next();
x
}
}
}
Some(x) => x
};
self.a_cur.as_ref().map(|a| (a.clone(), elt_b))
}
fn size_hint(&self) -> (usize, Option<usize>) {
let has_cur = self.a_cur.is_some() as usize;
// Not ExactSizeIterator because size may be larger than usize
let (b_min, b_max) = self.b.size_hint();
// Compute a * b_orig + b for both lower and upper bound
size_hint::add(
size_hint::mul(self.a.size_hint(), self.b_orig.size_hint()),
(b_min * has_cur, b_max.map(move |x| x * has_cur)))
}
fn fold<Acc, G>(mut self, mut accum: Acc, mut f: G) -> Acc
where G: FnMut(Acc, Self::Item) -> Acc,
{
// use a split loop to handle the loose a_cur as well as avoiding to
// clone b_orig at the end.
if let Some(mut a) = self.a_cur.take() {
let mut b = self.b;
loop {
accum = b.fold(accum, |acc, elt| f(acc, (a.clone(), elt)));
// we can only continue iterating a if we had a first element;
if let Some(next_a) = self.a.next() {
b = self.b_orig.clone();
a = next_a;
} else {
break;
}
}
}
accum
}
}
impl<I, J> FusedIterator for Product<I, J>
where I: FusedIterator,
J: Clone + FusedIterator,
I::Item: Clone
{}
/// A “meta iterator adaptor”. Its closure receives a reference to the iterator
/// and may pick off as many elements as it likes, to produce the next iterator element.
///
/// Iterator element type is *X*, if the return type of `F` is *Option\<X\>*.
///
/// See [`.batching()`](crate::Itertools::batching) for more information.
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Batching<I, F> {
f: F,
iter: I,
}
impl<I, F> fmt::Debug for Batching<I, F> where I: fmt::Debug {
debug_fmt_fields!(Batching, iter);
}
/// Create a new Batching iterator.
pub fn batching<I, F>(iter: I, f: F) -> Batching<I, F> {
Batching { f, iter }
}
impl<B, F, I> Iterator for Batching<I, F>
where I: Iterator,
F: FnMut(&mut I) -> Option<B>
{
type Item = B;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
(self.f)(&mut self.iter)
}
}
/// An iterator adaptor that steps a number elements in the base iterator
/// for each iteration.
///
/// The iterator steps by yielding the next element from the base iterator,
/// then skipping forward *n-1* elements.
///
/// See [`.step()`](crate::Itertools::step) for more information.
#[deprecated(note="Use std .step_by() instead", since="0.8.0")]
#[allow(deprecated)]
#[derive(Clone, Debug)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Step<I> {
iter: Fuse<I>,
skip: usize,
}
/// Create a `Step` iterator.
///
/// **Panics** if the step is 0.
#[allow(deprecated)]
pub fn step<I>(iter: I, step: usize) -> Step<I>
where I: Iterator
{
assert!(step != 0);
Step {
iter: iter.fuse(),
skip: step - 1,
}
}
#[allow(deprecated)]
impl<I> Iterator for Step<I>
where I: Iterator
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
let elt = self.iter.next();
if self.skip > 0 {
self.iter.nth(self.skip - 1);
}
elt
}
fn size_hint(&self) -> (usize, Option<usize>) {
let (low, high) = self.iter.size_hint();
let div = |x: usize| {
if x == 0 {
0
} else {
1 + (x - 1) / (self.skip + 1)
}
};
(div(low), high.map(div))
}
}
// known size
#[allow(deprecated)]
impl<I> ExactSizeIterator for Step<I>
where I: ExactSizeIterator
{}
pub trait MergePredicate<T> {
fn merge_pred(&mut self, a: &T, b: &T) -> bool;
}
#[derive(Clone, Debug)]
pub struct MergeLte;
impl<T: PartialOrd> MergePredicate<T> for MergeLte {
fn merge_pred(&mut self, a: &T, b: &T) -> bool {
a <= b
}
}
/// An iterator adaptor that merges the two base iterators in ascending order.
/// If both base iterators are sorted (ascending), the result is sorted.
///
/// Iterator element type is `I::Item`.
///
/// See [`.merge()`](crate::Itertools::merge_by) for more information.
pub type Merge<I, J> = MergeBy<I, J, MergeLte>;
/// Create an iterator that merges elements in `i` and `j`.
///
/// [`IntoIterator`] enabled version of [`Itertools::merge`](crate::Itertools::merge).
///
/// ```
/// use itertools::merge;
///
/// for elt in merge(&[1, 2, 3], &[2, 3, 4]) {
/// /* loop body */
/// }
/// ```
pub fn merge<I, J>(i: I, j: J) -> Merge<<I as IntoIterator>::IntoIter, <J as IntoIterator>::IntoIter>
where I: IntoIterator,
J: IntoIterator<Item = I::Item>,
I::Item: PartialOrd
{
merge_by_new(i, j, MergeLte)
}
/// An iterator adaptor that merges the two base iterators in ascending order.
/// If both base iterators are sorted (ascending), the result is sorted.
///
/// Iterator element type is `I::Item`.
///
/// See [`.merge_by()`](crate::Itertools::merge_by) for more information.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct MergeBy<I, J, F>
where I: Iterator,
J: Iterator<Item = I::Item>
{
a: Peekable<I>,
b: Peekable<J>,
fused: Option<bool>,
cmp: F,
}
impl<I, J, F> fmt::Debug for MergeBy<I, J, F>
where I: Iterator + fmt::Debug, J: Iterator<Item = I::Item> + fmt::Debug,
I::Item: fmt::Debug,
{
debug_fmt_fields!(MergeBy, a, b);
}
impl<T, F: FnMut(&T, &T)->bool> MergePredicate<T> for F {
fn merge_pred(&mut self, a: &T, b: &T) -> bool {
self(a, b)
}
}
/// Create a `MergeBy` iterator.
pub fn merge_by_new<I, J, F>(a: I, b: J, cmp: F) -> MergeBy<I::IntoIter, J::IntoIter, F>
where I: IntoIterator,
J: IntoIterator<Item = I::Item>,
F: MergePredicate<I::Item>,
{
MergeBy {
a: a.into_iter().peekable(),
b: b.into_iter().peekable(),
fused: None,
cmp,
}
}
impl<I, J, F> Clone for MergeBy<I, J, F>
where I: Iterator,
J: Iterator<Item = I::Item>,
Peekable<I>: Clone,
Peekable<J>: Clone,
F: Clone
{
clone_fields!(a, b, fused, cmp);
}
impl<I, J, F> Iterator for MergeBy<I, J, F>
where I: Iterator,
J: Iterator<Item = I::Item>,
F: MergePredicate<I::Item>
{
type Item = I::Item;
fn next(&mut self) -> Option<Self::Item> {
let less_than = match self.fused {
Some(lt) => lt,
None => match (self.a.peek(), self.b.peek()) {
(Some(a), Some(b)) => self.cmp.merge_pred(a, b),
(Some(_), None) => {
self.fused = Some(true);
true
}
(None, Some(_)) => {
self.fused = Some(false);
false
}
(None, None) => return None,
}
};
if less_than {
self.a.next()
} else {
self.b.next()
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
// Not ExactSizeIterator because size may be larger than usize
size_hint::add(self.a.size_hint(), self.b.size_hint())
}
}
impl<I, J, F> FusedIterator for MergeBy<I, J, F>
where I: FusedIterator,
J: FusedIterator<Item = I::Item>,
F: MergePredicate<I::Item>
{}
/// An iterator adaptor that borrows from a `Clone`-able iterator
/// to only pick off elements while the predicate returns `true`.
///
/// See [`.take_while_ref()`](crate::Itertools::take_while_ref) for more information.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct TakeWhileRef<'a, I: 'a, F> {
iter: &'a mut I,
f: F,
}
impl<'a, I, F> fmt::Debug for TakeWhileRef<'a, I, F>
where I: Iterator + fmt::Debug,
{
debug_fmt_fields!(TakeWhileRef, iter);
}
/// Create a new `TakeWhileRef` from a reference to clonable iterator.
pub fn take_while_ref<I, F>(iter: &mut I, f: F) -> TakeWhileRef<I, F>
where I: Iterator + Clone
{
TakeWhileRef { iter, f }
}
impl<'a, I, F> Iterator for TakeWhileRef<'a, I, F>
where I: Iterator + Clone,
F: FnMut(&I::Item) -> bool
{
type Item = I::Item;
fn next(&mut self) -> Option<Self::Item> {
let old = self.iter.clone();
match self.iter.next() {
None => None,
Some(elt) => {
if (self.f)(&elt) {
Some(elt)
} else {
*self.iter = old;
None
}
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
(0, self.iter.size_hint().1)
}
}
/// An iterator adaptor that filters `Option<A>` iterator elements
/// and produces `A`. Stops on the first `None` encountered.
///
/// See [`.while_some()`](crate::Itertools::while_some) for more information.
#[derive(Clone, Debug)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct WhileSome<I> {
iter: I,
}
/// Create a new `WhileSome<I>`.
pub fn while_some<I>(iter: I) -> WhileSome<I> {
WhileSome { iter }
}
impl<I, A> Iterator for WhileSome<I>
where I: Iterator<Item = Option<A>>
{
type Item = A;
fn next(&mut self) -> Option<Self::Item> {
match self.iter.next() {
None | Some(None) => None,
Some(elt) => elt,
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
(0, self.iter.size_hint().1)
}
}
/// An iterator to iterate through all combinations in a `Clone`-able iterator that produces tuples
/// of a specific size.
///
/// See [`.tuple_combinations()`](crate::Itertools::tuple_combinations) for more
/// information.
#[derive(Clone, Debug)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct TupleCombinations<I, T>
where I: Iterator,
T: HasCombination<I>
{
iter: T::Combination,
_mi: PhantomData<I>,
}
pub trait HasCombination<I>: Sized {
type Combination: From<I> + Iterator<Item = Self>;
}
/// Create a new `TupleCombinations` from a clonable iterator.
pub fn tuple_combinations<T, I>(iter: I) -> TupleCombinations<I, T>
where I: Iterator + Clone,
I::Item: Clone,
T: HasCombination<I>,
{
TupleCombinations {
iter: T::Combination::from(iter),
_mi: PhantomData,
}
}
impl<I, T> Iterator for TupleCombinations<I, T>
where I: Iterator,
T: HasCombination<I>,
{
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
self.iter.next()
}
}
impl<I, T> FusedIterator for TupleCombinations<I, T>
where I: FusedIterator,
T: HasCombination<I>,
{}
#[derive(Clone, Debug)]
pub struct Tuple1Combination<I> {
iter: I,
}
impl<I> From<I> for Tuple1Combination<I> {
fn from(iter: I) -> Self {
Tuple1Combination { iter }
}
}
impl<I: Iterator> Iterator for Tuple1Combination<I> {
type Item = (I::Item,);
fn next(&mut self) -> Option<Self::Item> {
self.iter.next().map(|x| (x,))
}
}
impl<I: Iterator> HasCombination<I> for (I::Item,) {
type Combination = Tuple1Combination<I>;
}
macro_rules! impl_tuple_combination {
($C:ident $P:ident ; $($X:ident)*) => (
#[derive(Clone, Debug)]
pub struct $C<I: Iterator> {
item: Option<I::Item>,
iter: I,
c: $P<I>,
}
impl<I: Iterator + Clone> From<I> for $C<I> {
fn from(mut iter: I) -> Self {
Self {
item: iter.next(),
iter: iter.clone(),
c: iter.into(),
}
}
}
impl<I: Iterator + Clone> From<I> for $C<Fuse<I>> {
fn from(iter: I) -> Self {
Self::from(iter.fuse())
}
}
impl<I, A> Iterator for $C<I>
where I: Iterator<Item = A> + Clone,
I::Item: Clone
{
type Item = (A, $(ignore_ident!($X, A)),*);
fn next(&mut self) -> Option<Self::Item> {
if let Some(($($X),*,)) = self.c.next() {
let z = self.item.clone().unwrap();
Some((z, $($X),*))
} else {
self.item = self.iter.next();
self.item.clone().and_then(|z| {
self.c = self.iter.clone().into();
self.c.next().map(|($($X),*,)| (z, $($X),*))
})
}
}
}
impl<I, A> HasCombination<I> for (A, $(ignore_ident!($X, A)),*)
where I: Iterator<Item = A> + Clone,
I::Item: Clone
{
type Combination = $C<Fuse<I>>;
}
)
}
// This snippet generates the twelve `impl_tuple_combination!` invocations:
// use core::iter;
// use itertools::Itertools;
//
// for i in 2..=12 {
// println!("impl_tuple_combination!(Tuple{arity}Combination Tuple{prev}Combination; {idents});",
// arity = i,
// prev = i - 1,
// idents = ('a'..'z').take(i - 1).join(" "),
// );
// }
// It could probably be replaced by a bit more macro cleverness.
impl_tuple_combination!(Tuple2Combination Tuple1Combination; a);
impl_tuple_combination!(Tuple3Combination Tuple2Combination; a b);
impl_tuple_combination!(Tuple4Combination Tuple3Combination; a b c);
impl_tuple_combination!(Tuple5Combination Tuple4Combination; a b c d);
impl_tuple_combination!(Tuple6Combination Tuple5Combination; a b c d e);
impl_tuple_combination!(Tuple7Combination Tuple6Combination; a b c d e f);
impl_tuple_combination!(Tuple8Combination Tuple7Combination; a b c d e f g);
impl_tuple_combination!(Tuple9Combination Tuple8Combination; a b c d e f g h);
impl_tuple_combination!(Tuple10Combination Tuple9Combination; a b c d e f g h i);
impl_tuple_combination!(Tuple11Combination Tuple10Combination; a b c d e f g h i j);
impl_tuple_combination!(Tuple12Combination Tuple11Combination; a b c d e f g h i j k);
/// An iterator adapter to filter values within a nested `Result::Ok`.
///
/// See [`.filter_ok()`](crate::Itertools::filter_ok) for more information.
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct FilterOk<I, F> {
iter: I,
f: F
}
impl<I, F> fmt::Debug for FilterOk<I, F>
where
I: fmt::Debug,
{
debug_fmt_fields!(FilterOk, iter);
}
/// Create a new `FilterOk` iterator.
pub fn filter_ok<I, F, T, E>(iter: I, f: F) -> FilterOk<I, F>
where I: Iterator<Item = Result<T, E>>,
F: FnMut(&T) -> bool,
{
FilterOk {
iter,
f,
}
}
impl<I, F, T, E> Iterator for FilterOk<I, F>
where I: Iterator<Item = Result<T, E>>,
F: FnMut(&T) -> bool,
{
type Item = Result<T, E>;
fn next(&mut self) -> Option<Self::Item> {
loop {
match self.iter.next() {
Some(Ok(v)) => {
if (self.f)(&v) {
return Some(Ok(v));
}
},
Some(Err(e)) => return Some(Err(e)),
None => return None,
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
(0, self.iter.size_hint().1)
}
fn fold<Acc, Fold>(self, init: Acc, fold_f: Fold) -> Acc
where Fold: FnMut(Acc, Self::Item) -> Acc,
{
let mut f = self.f;
self.iter.filter(|v| {
v.as_ref().map(&mut f).unwrap_or(true)
}).fold(init, fold_f)
}
fn collect<C>(self) -> C
where C: FromIterator<Self::Item>
{
let mut f = self.f;
self.iter.filter(|v| {
v.as_ref().map(&mut f).unwrap_or(true)
}).collect()
}
}
impl<I, F, T, E> FusedIterator for FilterOk<I, F>
where I: FusedIterator<Item = Result<T, E>>,
F: FnMut(&T) -> bool,
{}
/// An iterator adapter to filter and apply a transformation on values within a nested `Result::Ok`.
///
/// See [`.filter_map_ok()`](crate::Itertools::filter_map_ok) for more information.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct FilterMapOk<I, F> {
iter: I,
f: F
}
impl<I, F> fmt::Debug for FilterMapOk<I, F>
where
I: fmt::Debug,
{
debug_fmt_fields!(FilterMapOk, iter);
}
fn transpose_result<T, E>(result: Result<Option<T>, E>) -> Option<Result<T, E>> {
match result {
Ok(Some(v)) => Some(Ok(v)),
Ok(None) => None,
Err(e) => Some(Err(e)),
}
}
/// Create a new `FilterOk` iterator.
pub fn filter_map_ok<I, F, T, U, E>(iter: I, f: F) -> FilterMapOk<I, F>
where I: Iterator<Item = Result<T, E>>,
F: FnMut(T) -> Option<U>,
{
FilterMapOk {
iter,
f,
}
}
impl<I, F, T, U, E> Iterator for FilterMapOk<I, F>
where I: Iterator<Item = Result<T, E>>,
F: FnMut(T) -> Option<U>,
{
type Item = Result<U, E>;
fn next(&mut self) -> Option<Self::Item> {
loop {
match self.iter.next() {
Some(Ok(v)) => {
if let Some(v) = (self.f)(v) {
return Some(Ok(v));
}
},
Some(Err(e)) => return Some(Err(e)),
None => return None,
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
(0, self.iter.size_hint().1)
}
fn fold<Acc, Fold>(self, init: Acc, fold_f: Fold) -> Acc
where Fold: FnMut(Acc, Self::Item) -> Acc,
{
let mut f = self.f;
self.iter.filter_map(|v| {
transpose_result(v.map(&mut f))
}).fold(init, fold_f)
}
fn collect<C>(self) -> C
where C: FromIterator<Self::Item>
{
let mut f = self.f;
self.iter.filter_map(|v| {
transpose_result(v.map(&mut f))
}).collect()
}
}
impl<I, F, T, U, E> FusedIterator for FilterMapOk<I, F>
where I: FusedIterator<Item = Result<T, E>>,
F: FnMut(T) -> Option<U>,
{}
/// An iterator adapter to get the positions of each element that matches a predicate.
///
/// See [`.positions()`](crate::Itertools::positions) for more information.
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Positions<I, F> {
iter: I,
f: F,
count: usize,
}
impl<I, F> fmt::Debug for Positions<I, F>
where
I: fmt::Debug,
{
debug_fmt_fields!(Positions, iter, count);
}
/// Create a new `Positions` iterator.
pub fn positions<I, F>(iter: I, f: F) -> Positions<I, F>
where I: Iterator,
F: FnMut(I::Item) -> bool,
{
Positions {
iter,
f,
count: 0
}
}
impl<I, F> Iterator for Positions<I, F>
where I: Iterator,
F: FnMut(I::Item) -> bool,
{
type Item = usize;
fn next(&mut self) -> Option<Self::Item> {
while let Some(v) = self.iter.next() {
let i = self.count;
self.count = i + 1;
if (self.f)(v) {
return Some(i);
}
}
None
}
fn size_hint(&self) -> (usize, Option<usize>) {
(0, self.iter.size_hint().1)
}
}
impl<I, F> DoubleEndedIterator for Positions<I, F>
where I: DoubleEndedIterator + ExactSizeIterator,
F: FnMut(I::Item) -> bool,
{
fn next_back(&mut self) -> Option<Self::Item> {
while let Some(v) = self.iter.next_back() {
if (self.f)(v) {
return Some(self.count + self.iter.len())
}
}
None
}
}
impl<I, F> FusedIterator for Positions<I, F>
where I: FusedIterator,
F: FnMut(I::Item) -> bool,
{}
/// An iterator adapter to apply a mutating function to each element before yielding it.
///
/// See [`.update()`](crate::Itertools::update) for more information.
#[derive(Clone)]
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
pub struct Update<I, F> {
iter: I,
f: F,
}
impl<I, F> fmt::Debug for Update<I, F>
where
I: fmt::Debug,
{
debug_fmt_fields!(Update, iter);
}
/// Create a new `Update` iterator.
pub fn update<I, F>(iter: I, f: F) -> Update<I, F>
where
I: Iterator,
F: FnMut(&mut I::Item),
{
Update { iter, f }
}
impl<I, F> Iterator for Update<I, F>
where
I: Iterator,
F: FnMut(&mut I::Item),
{
type Item = I::Item;
fn next(&mut self) -> Option<Self::Item> {
if let Some(mut v) = self.iter.next() {
(self.f)(&mut v);
Some(v)
} else {
None
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
fn fold<Acc, G>(self, init: Acc, mut g: G) -> Acc
where G: FnMut(Acc, Self::Item) -> Acc,
{
let mut f = self.f;
self.iter.fold(init, move |acc, mut v| { f(&mut v); g(acc, v) })
}
// if possible, re-use inner iterator specializations in collect
fn collect<C>(self) -> C
where C: FromIterator<Self::Item>
{
let mut f = self.f;
self.iter.map(move |mut v| { f(&mut v); v }).collect()
}
}
impl<I, F> ExactSizeIterator for Update<I, F>
where
I: ExactSizeIterator,
F: FnMut(&mut I::Item),
{}
impl<I, F> DoubleEndedIterator for Update<I, F>
where
I: DoubleEndedIterator,
F: FnMut(&mut I::Item),
{
fn next_back(&mut self) -> Option<Self::Item> {
if let Some(mut v) = self.iter.next_back() {
(self.f)(&mut v);
Some(v)
} else {
None
}
}
}
impl<I, F> FusedIterator for Update<I, F>
where
I: FusedIterator,
F: FnMut(&mut I::Item),
{}