We need to compare strings. We're not going to use std.mem.eql -- we'll write our own. It's five lines and we'll need something like it in our self-hosted compiler anyway.

fn streq(a: []const u8, b: []const u8) bool {
    if (a.len != b.len) {
        return false;
    }
    for (a, b) |ca, cb| {
        if (ca != cb) {
            return false;
        }
    }
    return true;
}

Test it in main: print("{}\n", .{streq("cat", "cat")}); -> true. print("{}\n", .{streq("cat", "dog")}); -> false.

We'll use streq everywhere we need to check for keywords like "var", "if", "while".