Macro konst::iter::into_iter

macro_rules! into_iter {
    ($iter:expr) => { ... };
}

Available on crate feature iter only.

Macro for converting ConstIntoIter implementors into const iterators.

Behavior

For std types (ConstIntoIter<Kind = IsStdKind>), this converts those types to their iterator. (example below)

For user-defined into-iterators (ConstIntoIter<Kind = IsIntoIterKind>), this calls their const_into_iter inherent method to convert them to an iterator. (example below)

For iterators (ConstIntoIter<Kind = IsIteratorKind>), this returns the iterator untouched. (example below)

Examples

Std type

This example demonstrates passing a ConstIntoIter<Kind = IsStdKind> in.

use konst::{iter, slice};

let mut elem;
let mut iter: slice::Iter<'_, u8> = iter::into_iter!(&[3, 5, 8]);

(elem, iter) = iter.next().unwrap();
assert_eq!(elem, &3);

(elem, iter) = iter.next().unwrap();
assert_eq!(elem, &5);

(elem, iter) = iter.next().unwrap();
assert_eq!(elem, &8);

assert!(iter.next().is_none());

IntoIterator type

This example demonstrates passing a ConstIntoIter<Kind = IsIntoIterKind> in.

use konst::{iter, string};

let mut iter: Countdown = iter::into_iter!(Number(3));
let mut elem;

(elem, iter) = iter.next().unwrap();
assert_eq!(elem, 2);

(elem, iter) = iter.next().unwrap();
assert_eq!(elem, 1);

(elem, iter) = iter.next().unwrap();
assert_eq!(elem, 0);

assert!(iter.next().is_none());


struct Number(u32);

impl iter::ConstIntoIter for Number {
    type Kind = iter::IsIntoIterKind;
    type Item = u32;
    type IntoIter = Countdown;
}

impl Number {
    const fn const_into_iter(self) -> Countdown {
        Countdown(self.0)
    }
}

struct Countdown(u32);

impl iter::ConstIntoIter for Countdown {
    type Kind = iter::IsIteratorKind;
    type Item = u32;
    type IntoIter = Self;
}

impl Countdown {
    const fn next(self) -> Option<(u32, Self)> {
        let next = konst::try_opt!(self.0.checked_sub(1));
        Some((next, Countdown(next)))
    }
}

Iterator type

This example demonstrates passing a ConstIntoIter<Kind = IsIteratorKind> in.

use konst::{iter, string};

let iter: string::Split<'_, '_, char> = string::split("foo bar baz", ' ');

// `iter::into_iter` is an identity function when passed iterators
let mut iter: string::Split<'_, '_, char> = iter::into_iter!(iter);
let mut elem;

(elem, iter) = iter.next().unwrap();
assert_eq!(elem, "foo");

(elem, iter) = iter.next().unwrap();
assert_eq!(elem, "bar");

(elem, iter) = iter.next().unwrap();
assert_eq!(elem, "baz");

assert!(iter.next().is_none());