diff --git a/src/tuple_impl.rs b/src/tuple_impl.rs
index 8f14845df..1d24b0bb3 100644
--- a/src/tuple_impl.rs
+++ b/src/tuple_impl.rs
@@ -244,15 +244,32 @@ pub trait TupleCollect: Sized {
fn left_shift_push(&mut self, item: Self::Item);
}
+macro_rules! count_ident{
+ () => {0};
+ ($i0:ident, $($i:ident,)*) => {1 + count_ident!($($i,)*)};
+}
+macro_rules! ignore_ident{
+ ($id:ident, $($t:tt)*) => {$($t)*};
+}
+macro_rules! rev_for_each_ident{
+ ($m:ident, ) => {};
+ ($m:ident, $i0:ident, $($i:ident,)*) => {
+ rev_for_each_ident!($m, $($i,)*);
+ $m!($i0);
+ };
+}
+
macro_rules! impl_tuple_collect {
- ($N:expr; $A:ident ; $($X:ident),* ; $($Y:ident),* ; $($Y_rev:ident),*) => (
- impl<$A> TupleCollect for ($($X),*,) {
- type Item = $A;
- type Buffer = [Option<$A>; $N - 1];
+ ($dummy:ident,) => {}; // stop
+ ($dummy:ident, $($Y:ident,)*) => (
+ impl_tuple_collect!($($Y,)*);
+ impl TupleCollect for ($(ignore_ident!($Y, A),)*) {
+ type Item = A;
+ type Buffer = [Option; count_ident!($($Y,)*) - 1];
#[allow(unused_assignments, unused_mut)]
fn collect_from_iter(iter: I, buf: &mut Self::Buffer) -> Option
- where I: IntoIterator-
+ where I: IntoIterator
-
{
let mut iter = iter.into_iter();
$(
@@ -281,7 +298,7 @@ macro_rules! impl_tuple_collect {
}
fn collect_from_iter_no_buf(iter: I) -> Option
- where I: IntoIterator
-
+ where I: IntoIterator
-
{
let mut iter = iter.into_iter();
@@ -291,44 +308,20 @@ macro_rules! impl_tuple_collect {
}
fn num_items() -> usize {
- $N
+ count_ident!($($Y,)*)
}
- fn left_shift_push(&mut self, item: $A) {
+ fn left_shift_push(&mut self, mut item: A) {
use std::mem::replace;
let &mut ($(ref mut $Y),*,) = self;
- $(
- let item = replace($Y_rev, item);
- )*
+ macro_rules! replace_item{($i:ident) => {
+ item = replace($i, item);
+ }};
+ rev_for_each_ident!(replace_item, $($Y,)*);
drop(item);
}
}
)
}
-
-// This snippet generates the twelve `impl_tuple_collect!` invocations:
-// use core::iter;
-// use itertools::Itertools;
-//
-// for i in 1..=12 {
-// println!("impl_tuple_collect!({arity}; A; {ty}; {idents}; {rev_idents});",
-// arity=i,
-// ty=iter::repeat("A").take(i).join(", "),
-// idents=('a'..='z').take(i).join(", "),
-// rev_idents=('a'..='z').take(i).collect_vec().into_iter().rev().join(", ")
-// );
-// }
-// It could probably be replaced by a bit more macro cleverness.
-impl_tuple_collect!(1; A; A; a; a);
-impl_tuple_collect!(2; A; A, A; a, b; b, a);
-impl_tuple_collect!(3; A; A, A, A; a, b, c; c, b, a);
-impl_tuple_collect!(4; A; A, A, A, A; a, b, c, d; d, c, b, a);
-impl_tuple_collect!(5; A; A, A, A, A, A; a, b, c, d, e; e, d, c, b, a);
-impl_tuple_collect!(6; A; A, A, A, A, A, A; a, b, c, d, e, f; f, e, d, c, b, a);
-impl_tuple_collect!(7; A; A, A, A, A, A, A, A; a, b, c, d, e, f, g; g, f, e, d, c, b, a);
-impl_tuple_collect!(8; A; A, A, A, A, A, A, A, A; a, b, c, d, e, f, g, h; h, g, f, e, d, c, b, a);
-impl_tuple_collect!(9; A; A, A, A, A, A, A, A, A, A; a, b, c, d, e, f, g, h, i; i, h, g, f, e, d, c, b, a);
-impl_tuple_collect!(10; A; A, A, A, A, A, A, A, A, A, A; a, b, c, d, e, f, g, h, i, j; j, i, h, g, f, e, d, c, b, a);
-impl_tuple_collect!(11; A; A, A, A, A, A, A, A, A, A, A, A; a, b, c, d, e, f, g, h, i, j, k; k, j, i, h, g, f, e, d, c, b, a);
-impl_tuple_collect!(12; A; A, A, A, A, A, A, A, A, A, A, A, A; a, b, c, d, e, f, g, h, i, j, k, l; l, k, j, i, h, g, f, e, d, c, b, a);
+impl_tuple_collect!(dummy, a, b, c, d, e, f, g, h, i, j, k, l,);