Const arguments

[Centril]

I think the notion that you can add dependent types without changing / expanding the mental model is mistaken personally.

@newpavlov

fn create_2d_array(const columns: usize, const rows: usize)
    -> [[u32; columns]; rows] { .. }

// well, looks nice and clear!
// Some even can forget about const sizes of the array for a moment.
let foo = create_2d_array(10, 3);

Even better:

fn create_2d_array<const columns: usize, const rows: usize>()
    -> [[u32; columns]; rows] { .. }

let foo = create_2d_array(); // Sizes are inferred.

@newpavlov

// ehm.. is `f32` a typo? shouldn't it be `0f32` or something?

Clearly that can't be true. The function signature explicitly states that T is a type.

@newpavlov

It is just about expectations, in function arguments you expect values, not types. And breaking this expectation will cause a substantial dissonance.

I think similarly there is an expectation that you only have types (and lifetimes) in <T, ..>, and permitting <const N: usize> breaks that by allowing values within <..>. My view is that both expectations need to be adjusted once you're in a (const) dependently typed language.