Function konst::slice::try_into_array

pub const fn try_into_array<T, const N: usize>(
    slice: &[T]
) -> Result<&[T; N], TryIntoArrayError>

This is supported on crate feature deref_raw_in_fn only.

Tries to convert from &[T] to &[T; N], usable in const fns. Requires Rust nightly.

Returns an Err(TryIntoArrayError{..}) when the slice doesn’t match the expected length.

For an alternative that works on stable Rust, there is the try_into_array macro, but it can only be used in consts, not in const fns .

Features

This is not enabled by default, you need to enable the "deref_raw_in_fn" feature to use it, which requires Rust nightly.

Example

use konst::{
    slice::{TryIntoArrayError, try_into_array},
    result,
    unwrap_ctx,
};


const fn arr_5() -> Option<&'static [u64; 5]> {
    let slice: &[u64] = &[1, 10, 100, 1000, 10000];

    // Passing the length explicitly to the function
    result::ok!(try_into_array::<_, 5>(slice))
}

assert_eq!(arr_5(), Some(&[1, 10, 100, 1000, 10000]));


const fn err() -> Result<&'static [u64; 5], TryIntoArrayError> {
    let slice: &[u64] = &[];

    // Letting the function infer the length of the array,
    try_into_array(slice)
}

assert!(err().is_err());


const fn arr_3() -> &'static [u64; 3] {
    let slice: &[u64] = &[3, 5, 8];

    let array = unwrap_ctx!(try_into_array(slice));
     
    // You can destructure the array into its elements like this
    let [a, b, c] = *array;
     
    array
}

assert_eq!(arr_3(), &[3, 5, 8]);