How to construct large const arrays in Rust without manually writing values to construct it-CodePudding

TLDR: What is the best way to construct large const arrays without writing all the values manually one by one.

Subjective question below:

I want my program to have an const array that will hold range of ASCII bytes ([u8; 94]), but I don't want to use Range<u8>.

And the reason I am not using Vec is because I already know the exact range of values I can do it all statically, and I just can't seem to find the way to construct such an array without manually writing each value.

What I did before posting this question was use const Range because contains is O(1).

Anyways regarding original problem, I want this:

const VALID_BLOCK_BYTES: [u8; 94] = [32..126; 94];

How do I get constant variable array with values from 32 up to 126 without manually writing it myself?

CodePudding user response：

I think the best way to achieve this right now is with a manual loop:

const VALID_BLOCK_BYTES: [u8; 94] = {
    let mut output = [0; 94];
    
    let mut i = 0;
    while i < 94 {
        output[i as usize] = i   32;
        i  = 1;
    }

    output
};

Can't use iterators because traits in const contexts aren't stable.

You can, of course, factor that out into a const fn if you need to do that a lot.