> On Jun 6, 2025, at 21:53, ToddAndMargo via perl6-users <perl6-users@perl.org>
> wrote:
>
> Hi All,
>
> Is there an easy way to print ones' and two's compliment
> of a 32 bit integer?
>
> Many thanks,
> -T
>
>
> sub ones-complement(Int $num) {
> my $binary = $num.base(2);
> my $complement = '';
> for $binary.comb -> $bit {
> $complement ~= $bit eq '0' ?? '1' !! '0';
> }
> return $complement;
> }
>
> my $number = 5;
> my $complement = ones-complement($number);
> print "Ones complement of $number is $complement\n";
>
>
> seems a bit much:
> https://search.brave.com/search?q=raku+print+ones+compliment&source=web&summary=1&conversation=00fda578d0badafdf15143
Seems wrong, too.
1. The code in `sub ones-complement`:
A. ends in `return $complement`, but should probably end in `return
$complement.parse-base(2)`.
B. could be shortened to `$num.base(2).trans(<0 1>=><1
0>).parse-base(2)`.
C. Gives the same result of `2` (or binary "010") for inputs of
5,13,29,61..., which means it is not invertable, so it is probably not the
droids^Wcode you are looking for.
D. Might be saved by changing it to `(('0' x 32) ~
$num.base(2)).substr(*-32).trans(<0 1> => <1 0>).parse-base(2)`, but there is
no need, because:
2. Raku has twos-complement built-in, via prefix `+^`. (Not *infix* `+^`,
which would be numeric `xor`).
A. So: `sub twos-complement (Int $num) { return +^ $num }`
B. `sub ones-complement (Int $num) { return 1 +
twos-complement($num) }` # Or would it be `-1` when negative? Depends on if you
are doing `int` or `uint`? Unsure right now.
See also:
https://docs.raku.org/language/operators#prefix_+^
https://rosettacode.org/wiki/Bitwise_operations#Raku
https://raku.land/zef:thundergnat/FixedInt
--
Hope this helps (but I am very sick with a 72-hour bug, so I may have missed
something important),
Bruce Gray (Util of PerlMonks)
