[fpc-pascal] Bitcounting

[Jesus Reyes A.]

En Sat, 05 Mar 2016 12:03:24 -0600, Bart <bartjunk64 at gmail.com> escribió:

> Hi,
>
> Does FreePascal have a routine for counting bits?
> So that e.g. BitCount(%1001100100001) gives 5 (number of bits that are  
> 1)?
>
> I came up with (extracted from IntToBin()):
>
> function BitCount(N: Int64): Integer;
> var
>   Q: QWord;
>   i: Integer;
> begin
>   Result := 0;
>   Q := QWord(N);
>   for i := 0 to (8 * SizeOf(N) - 1) do
>   begin
>     if ((Q and 1) = 1) then Inc(Result);
>     Q := Q shr 1;
>   end;
> end;
>
> Surely this can be done better?
>
> Bart


function BitCount(N: Int64): Integer;
var
   i: Integer;
begin
   Result := 0;
   if N=0 then
     exit;
   for i := 0 to (8 * SizeOf(N) - 1) do
   begin
     if (N and (1 shl i)) <> 0 then Inc(result);
   end;
end;

not tested :D

Jesus Reyes A.