include "cowgol.coh";

sub gray_encode(n: uint8): (r: uint8) is
    r := n ^ n >> 1;
end sub;

sub gray_decode(n: uint8): (r: uint8) is
    r := n;
    while n > 0 loop
        n := n >> 1;
        r := r ^ n;
    end loop;
end sub;

sub print_binary(n: uint8) is
    var buf: uint8[9];
    var ptr := &buf[8];
    [ptr] := 0;
    loop
        ptr := @prev ptr;
        [ptr] := (n & 1) + '0';
        n := n >> 1;
        if n == 0 then break; end if;
    end loop;
    print(ptr);
end sub;

sub print_row(n: uint8) is
    print_i8(n);
    print(":\t");
    print_binary(n);
    print("\t=>\t");
    var gray_code := gray_encode(n);
    print_binary(gray_code);
    print("\t=>\t");
    var decoded := gray_decode(gray_code);
    print_i8(decoded);
    print_nl();
end sub;

var i: uint8 := 0;
while i <= 31 loop
    print_row(i);
    i := i + 1;
end loop;