std: add range(usize)

[nektro]

Many have requested an easier way to make an incrementing loop. In a way that doesn't dirty the namespace currently being worked in with an i variable with use of a while loop. Or suggesting a syntax change to the for loop or a new loop entirely. However, this is possible in userspace by taking advantage of the semantics of zero sized types.

As written in the doc comment it is used like so:

for (std.range(10)) |_, i| {
    // 'i' will increment from 0 -> 9
}

Justification: #358, #8292, and more

[andrewrk]

nah just use a while loop

[Jarred-Sumner]

This would be nice with inline when iterating through lists with comptime-known length but runtime-known values. That also avoids the overhead of creating a temporary array since it would do that at comptime

Before:

const unroll_count = comptime 64 / @sizeOf(PackageID);

while (remaining.len > unroll_count) {
    comptime var i: usize = 0;
    inline while (i < unroll_count) : (i += 1) {
        installer.installPackage(remaining[i], comptime log_level);
    }
    remaining = remaining[unroll_count..];
}

After:

const unroll_count = comptime 64 / @sizeOf(PackageID);

while (remaining.len > unroll_count) {
    inline for (std.range(unroll_count)) |i| {
        installer.installPackage(remaining[i], comptime log_level);
    }
    remaining = remaining[unroll_count..];
}

[nektro]

been available as a package at https://github.com/nektro/zig-range for some time now for anyone who still comes across this