Re: [fpc-pascal] Bitcounting

[Jesus Reyes A.]

En Sat, 05 Mar 2016 12:03:24 -0600, Bart <bartjun...@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.
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