arrayInfo programming

array_info.zig

const std = @import("std");

const ArrayInfo = struct {
    rank: usize,
    child: type,
};

fn arrayInfo(comptime artype: type) ArrayInfo {
    var rank: usize = 0;
    var currentType: type = artype;
    while (true) {
        switch (@typeInfo(currentType)) {
            .Array => |arinfo| {
                rank += 1;
                currentType = arinfo.child;
            },
            .Pointer => |ptinfo| {
                if (ptinfo.size == .Slice) {
                    rank += 1;
                    currentType = ptinfo.child;
                } else {
                    return ArrayInfo{ .rank = rank, .child = currentType };
                }
            },
            else => {
                return ArrayInfo{ .rank = rank, .child = currentType };
            },
        }
    }
}

const expectEqual = std.testing.expectEqual;

test "arrayInfo" {
    const a = [_]f64{ 1, 2, 3 };
    const b = [_][3]f64{
        .{ 1, 2, 3 },
        .{ 1, 2, 3 },
    };
    const c = b[0..2];

    expectEqual(arrayInfo(@TypeOf(a)), ArrayInfo{ .rank = 1, .child = f64 });
    expectEqual(arrayInfo(@TypeOf(b)), ArrayInfo{ .rank = 2, .child = f64 });
    expectEqual(arrayInfo(@TypeOf(c)), ArrayInfo{ .rank = 2, .child = f64 });
}

You could consider this complete if you're willing to handle non array type inputs to arrayInfo as rank zero arrays of the input type. That's probably more user friendly than a @compileError