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 #[allow(non_snake_case)]
26 impl<X, Iter, $($B),*> DoubleEndedIterator for ConsTuples<Iter, (($($B,)*), X)>
27 where Iter: DoubleEndedIterator<Item = (($($B,)*), X)>,
28 {
29 fn next_back(&mut self) -> Option<Self::Item> {
30 self.iter.next().map(|(($($B,)*), x)| ($($B,)* x, ))
31 }
32 }
33
34 );
35);
36
37impl_cons_iter!(A, B, C, D, E, F, G, H, I, J, K, L,);
38
39/// An iterator that maps an iterator of tuples like
40/// `((A, B), C)` to an iterator of `(A, B, C)`.
41///
42/// Used by the `iproduct!()` macro.
43#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
44#[derive(Debug)]
45pub struct ConsTuples<I, J>
46where
47 I: Iterator<Item = J>,
48{
49 iter: I,
50}
51
52impl<I, J> Clone for ConsTuples<I, J>
53where
54 I: Clone + Iterator<Item = J>,
55{
56 clone_fields!(iter);
57}
58
59/// Create an iterator that maps for example iterators of
60/// `((A, B), C)` to `(A, B, C)`.
61pub fn cons_tuples<I, J>(iterable: I) -> ConsTuples<I::IntoIter, J>
62where
63 I: IntoIterator<Item = J>,
64{
65 ConsTuples {
66 iter: iterable.into_iter(),
67 }
68}
69