I didn't understand how TBits.NotBits works.
Consider the following code:

   b:= TBits.Create(NRECORDS);
   b.NotBits(b);

or more clear:

   b:= TBits.Create(NRECORDS);
   b.Clearall;
   b.NotBits(b);

I supposed that all bits of b will be 1. What I obtain is that all bits are 0.

fpc 3.0.0 win64

Am I missing something?
Thank you.
Andrea Mauri

one more thing.
there is a method like clearall to set all bits to 1? clearall is much more faster then a simple iteration along all bits

Il 31/03/2017 14:07, Andrea Mauri ha scritto:

one last thing, using TBits it is possible to SetIndex in order to start from a predefined index when using FindNextBit and FindPrevBit Anyway it is possible to set the State only using FindFirstBit, so I cannot use FindNextBit only using SetIndex but I have to call also FindFirstBit.
Is it possible to introduce a SetState procedure?
Thanks again,
Andrea Mauri

Il 31/03/2017 14:10, Andrea Mauri ha scritto:

any answer?
I asked in the wrong place?
where should I ask?

Il 31/03/2017 14:10, Andrea Mauri ha scritto:

I didn't understand how TBits.NotBits works.

AFAIK a.NotBits(b) means (a and not b):

a b result
0 0 0
0 1 0
1 0 1
1 1 0

Mattias

Andrea Mauri wrote

any answer? I asked in the wrong place? where should I ask?

You asked in the right place. I just didn't notice your first mail.

I am not sure that what you did is supported.

b.notbits(b)

I am not sure that you can pass the same instance to b.

Can you test with 2 separate instances ?

Michael.

Just look at the code. It's only a few lines. It is supported.

Mattias

Thank you Mattias.
It works as you described.
Anyway, since ClearAll, AndBits, OrBits etc works iterating on FBits : ^TBitArray;
they are much faster then the simple iteration along property property Bits[Bit: longint]: Boolean read get write SetBit; default;

I think should be useful to have also at least two other methods directly implemented in tbits:
1. the opposite of ClearAll, something like SetAll that sets all bits to 1, I think this s a typical operation on Bits;

procedure TBits.Setall;
var
    loop : longint;
begin
    for loop := 0 to FSize - 1 do
       FBits^[loop] := 1;
end;
2. a Not operator, something like a.NotBits; with no arguments that
perform the not operation on the TBIts instance (a[i]:= not a[i]) or
something that performs a not operation on the passed TBits, i.e.
a.Not(b) that fills a in this way: a[i]:= not b[i];
procedure TBits.Notbits;
var
    n : longint;
    jj : cardinal;
    loop : longint;
begin
    for loop := 0 to FSize - 1 do
       FBits^[loop] := not FBits^[loop];
end;

or

procedure TBits.Not(bitset : TBits);
var
    n : longint;
    loop : longint;
begin
    if FSize < bitset.getFSize then
       n := FSize - 1
    else
       n := bitset.getFSize - 1;
    for loop := 0 to n do
       FBits^[loop] := not bitset.FBits^[loop];
end;

Should be
FBits^[loop] := not cardinal(0);

end;

Btw, it seems TBits misses an AssignBits(b: TBits).

And maybe an AssignNotBits(b: TBits)

"Not" is a preserved word.

For consistency with the other SomethingBits methods you must handle all bits, not just the start.

Mattias