itertools/
cons_tuples_impl.rs

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1
2macro_rules! impl_cons_iter(
3    ($_A:ident, $_B:ident, ) => (); // stop
4
5    ($A:ident, $($B:ident,)*) => (
6        impl_cons_iter!($($B,)*);
7        #[allow(non_snake_case)]
8        impl<X, Iter, $($B),*> Iterator for ConsTuples<Iter, (($($B,)*), X)>
9            where Iter: Iterator<Item = (($($B,)*), X)>,
10        {
11            type Item = ($($B,)* X, );
12            fn next(&mut self) -> Option<Self::Item> {
13                self.iter.next().map(|(($($B,)*), x)| ($($B,)* x, ))
14            }
15
16            fn size_hint(&self) -> (usize, Option<usize>) {
17                self.iter.size_hint()
18            }
19            fn fold<Acc, Fold>(self, accum: Acc, mut f: Fold) -> Acc
20                where Fold: FnMut(Acc, Self::Item) -> Acc,
21            {
22                self.iter.fold(accum, move |acc, (($($B,)*), x)| f(acc, ($($B,)* x, )))
23            }
24        }
25
26        #[allow(non_snake_case)]
27        impl<X, Iter, $($B),*> DoubleEndedIterator for ConsTuples<Iter, (($($B,)*), X)>
28            where Iter: DoubleEndedIterator<Item = (($($B,)*), X)>,
29        {
30            fn next_back(&mut self) -> Option<Self::Item> {
31                self.iter.next().map(|(($($B,)*), x)| ($($B,)* x, ))
32            }
33        }
34
35    );
36);
37
38impl_cons_iter!(A, B, C, D, E, F, G, H,);
39
40/// An iterator that maps an iterator of tuples like
41/// `((A, B), C)` to an iterator of `(A, B, C)`.
42///
43/// Used by the `iproduct!()` macro.
44#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
45#[derive(Debug)]
46pub struct ConsTuples<I, J>
47    where I: Iterator<Item=J>,
48{
49    iter: I,
50}
51
52impl<I, J> Clone for ConsTuples<I, J>
53    where I: Clone + Iterator<Item=J>,
54{
55    fn clone(&self) -> Self {
56        ConsTuples {
57            iter: self.iter.clone(),
58        }
59    }
60}
61
62/// Create an iterator that maps for example iterators of
63/// `((A, B), C)` to `(A, B, C)`.
64pub fn cons_tuples<I, J>(iterable: I) -> ConsTuples<I, J>
65    where I: Iterator<Item=J>
66{
67    ConsTuples { iter: iterable.into_iter() }
68}
itertools/cons_tuples_impl.rs

itertools/
cons_tuples_impl.rs
