arrayinit

A no-dependencies, no-std, stupidly simple and tiny crate for creating const-size arrays dynamically.

By default, when constructing an array [T; N], Rust allows only for two ways to initialize the array. For example, it allows naming all elements in the array like: [1, 2, 3, 4], or by giving a default value for all of the array entries ["Hello"; 5].

There are a few shortcomings to this approach - especially for generically-sized arrays. In particular, Rust at the moment, is not verbose enough initializing an array with differing values in such a case.

A major problem occurs when T is an owned type that doesn't implement Copy (for example, String type). Since N, the size of the array, is generically defined - we are forced to initialize the array with [concrete_value; N], which wouldn't compile since concrete_value is of type T which isn't Copy. In order to properly initialize such an array, ugly tricks are required.

This crate comes to solve this problem and allow for a more dynamic initialization very simply.

Example usage

There are multiple ways to use the arr! macro defined in this crate. The most generic way is by supplying a producer method, and giving the size of the array.

let array = arr![|idx| idx * 2; 4];
assert_eq!(array, [0, 2, 4, 6]);

Its also possible to omit the size of the array, and let the compiler figure it out on its own

let array = arr![|idx| idx * 2];

// We need to use the array somewhere to help the compiler understand whats its size should be
assert_eq!(array, [0, 2, 5, 6, 8, 10]);

If you feel like it, its also possible to initialize statically all elements:

let array = arr![1, 2, 3]; // Equivalent to `[1, 2, 3]`
assert_eq!(array, [1, 2, 3]);