itertools/
cons_tuples_impl.rs

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

itertools/
cons_tuples_impl.rs
