Module iterator_dsl

Documentation on the iterator DSL that some konst::iter macros support.

The macros from this crate don’t directly invoke any of the method listed below, they expand to equivalent code, this allows the macros to work on stable.

The collect_const macro is used in examples here purely for simplicity.

Methods

Every iterator method below behaves the same as in the Iterator trait, unless specified otherwise.

The methods listed alphabetically:

• copied
• enumerate
• filter_map
• filter
• flat_map
• flatten
• map
• rev
• skip_while
• skip
• take_while
• take
• zip

zip

Limitation: the iterator DSL can’t be passed as an argument to this method.

use konst::iter;

const ARR: [(&u8, usize); 4] =
    iter::collect_const!((&u8, usize) => &[3u8, 5, 8, 13],zip(100..));

assert_eq!(ARR, [(&3, 100), (&5, 101), (&8, 102), (&13, 103)]);

enumerate

enumerate always counts from 0, regardless of whether the iterator is reversed.

use konst::iter;

const ARR: [(usize, &u8); 4] =
    iter::collect_const!((usize, &u8) => &[3u8, 5, 8, 13],enumerate());

assert_eq!(ARR, [(0, &3), (1, &5), (2, &8), (3, &13)]);

filter

use konst::iter;

const ARR: [&u8; 4] = iter::collect_const!(&u8 =>
    &[3u8, 5, 8, 13, 21],
        filter(|e| !e.is_power_of_two()),
);

assert_eq!(ARR, [&3, &5, &13, &21]);

map

use konst::iter;

const ARR: [usize; 4] = iter::collect_const!(usize => (1..=4),map(|e| e * 3));

assert_eq!(ARR, [3, 6, 9, 12]);

filter_map

use konst::iter;

use std::num::NonZeroU8;

const ARR: [NonZeroU8; 4] = iter::collect_const!(NonZeroU8 =>
    &[3, 0, 1, 5, 6],
        filter_map(|x| NonZeroU8::new(*x)),
);

assert_eq!(ARR, [3, 1, 5, 6].map(|n| NonZeroU8::new(n).unwrap()));

flat_map

Limitation: the iterator DSL can’t be passed as an argument to this method.

use konst::iter;

const ARR: [usize; 9] = iter::collect_const!(usize =>
    &[3, 5, 8],
        flat_map(|x| {
            let x10 = *x * 10;
            x10..x10 + 3
        }),
);

assert_eq!(ARR, [30, 31, 32, 50, 51, 52, 80, 81, 82]);

flatten

use konst::iter;

const ARR: [&u8; 4] =
    iter::collect_const!(&u8 => &[&[3, 5], &[8, 13]], flatten());

assert_eq!(ARR, [&3, &5, &8, &13]);

copied

use konst::iter;

const ARR: [u8; 3] = iter::collect_const!(u8 =>
    &[2, 3, 4, 5, 6],
        copied(),
        filter(|n| *n % 2 == 0)
);

assert_eq!(ARR, [2, 4, 6]);

rev

Limitation: iterator-reversing methods can’t be called more than once in the same macro invocation.

use konst::iter;

const ARR: [&u8; 3] = iter::collect_const!(&u8 => &[2, 3, 5],rev());

assert_eq!(ARR, [&5, &3, &2]);

take

use konst::iter;

const ARR: [usize; 3] = iter::collect_const!(usize => 10..,take(3));

assert_eq!(ARR, [10, 11, 12]);

take_while

use konst::iter;

const ARR: [&u8; 4] = iter::collect_const!(&u8 =>
    &[3, 5, 8, 13, 21, 34, 55],take_while(|elem| **elem < 20 )
);

assert_eq!(ARR, [&3, &5, &8, &13]);

skip

use konst::iter;

const ARR: [usize; 3] = iter::collect_const!(usize => 10..=15,skip(3));

assert_eq!(ARR, [13, 14, 15]);

skip_while

use konst::iter;

const ARR: [&u8; 3] = iter::collect_const!(&u8 =>
    &[3, 5, 8, 13, 21, 34, 55],skip_while(|elem| **elem < 20 )
);

assert_eq!(ARR, [&21, &34, &55]);