Macro collect_const

macro_rules! collect_const {
    (
        $Item:ty =>
        $($rem:tt)*
    ) => { ... };
}

Collects an iterator constant into an array

Iterator methods

This macro supports emulating iterator methods by expanding to equivalent code.

The supported iterator methods are documented in the iterator_dsl module, because they are also supported by other konst::iter macros.

Syntax

The syntax of this macro is:

collect_const!(
    $Item:ty => $into_iterator:expr
        $(, $iterator_method:ident ($($method_args:tt)*) )*
        $(,)?
)

Where $Item is the type of the elements that’ll be collected into an array.

Where $into_iterator is any type that can be converted into a const iterator, with konst::iter::into_iter.

Where $iterator_method is any of the supported methods described in the iterator_dsl module.

Examples

Iterating over a range

use konst::iter;

const ARR: [u64; 8] = iter::collect_const!(u64 =>
    10..,
        filter(|n| *n % 2 == 0),
        skip(5),
        take(8),
);

assert_eq!(ARR, [20, 22, 24, 26, 28, 30, 32, 34]);

Iterating over an array

use konst::iter;

const ARR: [u8; 6] = iter::collect_const!(u8 =>
    // the `&` is required here,
    // because by-value iteration over arrays is not supported.
    &[10, 20, 30],
        flat_map(|&n| {
            // To allow returning references to arrays, the macro extends 
            // the lifetime of borrows to temporaries in return position.
            // The lifetime of the array is extended to the entire iterator chain.
            &[n - 1, n + 1]
        }),
        copied()
);

assert_eq!(ARR, [9, 11, 19, 21, 29, 31]);