/rust/registry/src/index.crates.io-6f17d22bba15001f/itertools-0.12.1/src/intersperse.rs

Source (jump to first uncovered line)
use super::size_hint;
use std::iter::{Fuse, FusedIterator};

pub trait IntersperseElement<Item> {
    fn generate(&mut self) -> Item;
}

#[derive(Debug, Clone)]
pub struct IntersperseElementSimple<Item>(Item);

impl<Item: Clone> IntersperseElement<Item> for IntersperseElementSimple<Item> {
    fn generate(&mut self) -> Item {
        self.0.clone()
    }
}

/// An iterator adaptor to insert a particular value
/// between each element of the adapted iterator.
///
/// Iterator element type is `I::Item`
///
/// This iterator is *fused*.
///
/// See [`.intersperse()`](crate::Itertools::intersperse) for more information.
pub type Intersperse<I> = IntersperseWith<I, IntersperseElementSimple<<I as Iterator>::Item>>;

/// Create a new Intersperse iterator
pub fn intersperse<I>(iter: I, elt: I::Item) -> Intersperse<I>
where
    I: Iterator,
{
    intersperse_with(iter, IntersperseElementSimple(elt))
}

impl<Item, F: FnMut() -> Item> IntersperseElement<Item> for F {
    fn generate(&mut self) -> Item {
        self()
    }
}

/// An iterator adaptor to insert a particular value created by a function
/// between each element of the adapted iterator.
///
/// Iterator element type is `I::Item`
///
/// This iterator is *fused*.
///
/// See [`.intersperse_with()`](crate::Itertools::intersperse_with) for more information.
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone, Debug)]
pub struct IntersperseWith<I, ElemF>
where
    I: Iterator,
{
    element: ElemF,
    iter: Fuse<I>,
    /// `peek` is None while no item have been taken out of `iter` (at definition).
    /// Then `peek` will alternatively be `Some(None)` and `Some(Some(item))`,
    /// where `None` indicates it's time to generate from `element` (unless `iter` is empty).
    peek: Option<Option<I::Item>>,
}

/// Create a new `IntersperseWith` iterator
pub fn intersperse_with<I, ElemF>(iter: I, elt: ElemF) -> IntersperseWith<I, ElemF>
where
    I: Iterator,
{
    IntersperseWith {
        peek: None,
        iter: iter.fuse(),
        element: elt,
    }
}

impl<I, ElemF> Iterator for IntersperseWith<I, ElemF>
where
    I: Iterator,
    ElemF: IntersperseElement<I::Item>,
{
    type Item = I::Item;
    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        let Self {
            element,
            iter,
            peek,
        } = self;
        match peek {
            Some(item @ Some(_)) => item.take(),
            Some(None) => match iter.next() {
                new @ Some(_) => {
                    *peek = Some(new);
                    Some(element.generate())
                }
                None => None,
            },
            None => {
                *peek = Some(None);
                iter.next()
            }
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let mut sh = self.iter.size_hint();
        sh = size_hint::add(sh, sh);
        match self.peek {
            Some(Some(_)) => size_hint::add_scalar(sh, 1),
            Some(None) => sh,
            None => size_hint::sub_scalar(sh, 1),
        }
    }

    fn fold<B, F>(self, init: B, mut f: F) -> B
    where
        Self: Sized,
        F: FnMut(B, Self::Item) -> B,
    {
        let Self {
            mut element,
            mut iter,
            peek,
        } = self;
        let mut accum = init;

        if let Some(x) = peek.unwrap_or_else(|| iter.next()) {
            accum = f(accum, x);
        }

        iter.fold(accum, |accum, x| {
            let accum = f(accum, element.generate());
            f(accum, x)
        })
    }
}

impl<I, ElemF> FusedIterator for IntersperseWith<I, ElemF>
where
    I: Iterator,
    ElemF: IntersperseElement<I::Item>,
{
}

Line	Count	Source (jump to first uncovered line)
1		use super::size_hint;
2		use std::iter::{Fuse, FusedIterator};
3
4		pub trait IntersperseElement<Item> {
5		fn generate(&mut self) -> Item;
6		}
7
8		#[derive(Debug, Clone)]
9		pub struct IntersperseElementSimple<Item>(Item);
10
11		impl<Item: Clone> IntersperseElement<Item> for IntersperseElementSimple<Item> {
12	0	fn generate(&mut self) -> Item {
13	0	self.0.clone()
14	0	}
15		}
16
17		/// An iterator adaptor to insert a particular value
18		/// between each element of the adapted iterator.
19		///
20		/// Iterator element type is `I::Item`
21		///
22		/// This iterator is fused.
23		///
24		/// See [`.intersperse()`](crate::Itertools::intersperse) for more information.
25		pub type Intersperse<I> = IntersperseWith<I, IntersperseElementSimple<<I as Iterator>::Item>>;
26
27		/// Create a new Intersperse iterator
28	0	pub fn intersperse<I>(iter: I, elt: I::Item) -> Intersperse<I>
29	0	where
30	0	I: Iterator,
31	0	{
32	0	intersperse_with(iter, IntersperseElementSimple(elt))
33	0	}
34
35		impl<Item, F: FnMut() -> Item> IntersperseElement<Item> for F {
36	0	fn generate(&mut self) -> Item {
37	0	self()
38	0	}
39		}
40
41		/// An iterator adaptor to insert a particular value created by a function
42		/// between each element of the adapted iterator.
43		///
44		/// Iterator element type is `I::Item`
45		///
46		/// This iterator is fused.
47		///
48		/// See [`.intersperse_with()`](crate::Itertools::intersperse_with) for more information.
49		#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
50		#[derive(Clone, Debug)]
51		pub struct IntersperseWith<I, ElemF>
52		where
53		I: Iterator,
54		{
55		element: ElemF,
56		iter: Fuse<I>,
57		/// `peek` is None while no item have been taken out of `iter` (at definition).
58		/// Then `peek` will alternatively be `Some(None)` and `Some(Some(item))`,
59		/// where `None` indicates it's time to generate from `element` (unless `iter` is empty).
60		peek: Option<Option<I::Item>>,
61		}
62
63		/// Create a new `IntersperseWith` iterator
64	0	pub fn intersperse_with<I, ElemF>(iter: I, elt: ElemF) -> IntersperseWith<I, ElemF>
65	0	where
66	0	I: Iterator,
67	0	{
68	0	IntersperseWith {
69	0	peek: None,
70	0	iter: iter.fuse(),
71	0	element: elt,
72	0	}
73	0	}
74
75		impl<I, ElemF> Iterator for IntersperseWith<I, ElemF>
76		where
77		I: Iterator,
78		ElemF: IntersperseElement<I::Item>,
79		{
80		type Item = I::Item;
81		#[inline]
82	0	fn next(&mut self) -> Option<Self::Item> {
83	0	let Self {
84	0	element,
85	0	iter,
86	0	peek,
87	0	} = self;
88	0	match peek {
89	0	Some(item @ Some(_)) => item.take(),
90	0	Some(None) => match iter.next() {
91	0	new @ Some(_) => {
92	0	*peek = Some(new);
93	0	Some(element.generate())
94		}
95	0	None => None,
96		},
97		None => {
98	0	*peek = Some(None);
99	0	iter.next()
100		}
101		}
102	0	}
103
104	0	fn size_hint(&self) -> (usize, Option<usize>) {
105	0	let mut sh = self.iter.size_hint();
106	0	sh = size_hint::add(sh, sh);
107	0	match self.peek {
108	0	Some(Some(_)) => size_hint::add_scalar(sh, 1),
109	0	Some(None) => sh,
110	0	None => size_hint::sub_scalar(sh, 1),
111		}
112	0	}
113
114	0	fn fold<B, F>(self, init: B, mut f: F) -> B
115	0	where
116	0	Self: Sized,
117	0	F: FnMut(B, Self::Item) -> B,
118	0	{
119	0	let Self {
120	0	mut element,
121	0	mut iter,
122	0	peek,
123	0	} = self;
124	0	let mut accum = init;
125
126	0	if let Some(x) = peek.unwrap_or_else(\|\| iter.next()) {
127	0	accum = f(accum, x);
128	0	}
129
130	0	iter.fold(accum, \|accum, x\| {
131	0	let accum = f(accum, element.generate());
132	0	f(accum, x)
133	0	})
134	0	}
135		}
136
137		impl<I, ElemF> FusedIterator for IntersperseWith<I, ElemF>
138		where
139		I: Iterator,
140		ElemF: IntersperseElement<I::Item>,
141		{
142		}

Coverage Report

Created: 2025-07-01 06:50