[fpc-devel] about commit r29324

[Michael Van Canneyt]

On Sun, 28 Dec 2014, Mattias Gaertner wrote:

> Hi,
>
> forwarded from Zeljko:
>
> It's about fpc issue
> http://bugs.freepascal.org/view.php?id=26370
>
> It seems that TVariantArrayIterator.AtEnd loops for all Dims for no reason, so have
> impact on performance.
>
> *current implementation*
> function TVariantArrayIterator.AtEnd: Boolean;
> var
>   i : sizeint;
> begin
>   result:=false;
>   for i:=0 to Pred(Dims) do
>     if Coords^[i] >= Bounds^[i].LowBound + Bounds^[i].ElementCount then
>       result:=true;
> end;
>
> *optimized implementation*
> function TVariantArrayIterator.AtEnd: Boolean;
> var
>   i : sizeint;
> begin
>   result:=false;
>   for i:=0 to Pred(Dims) do
>     if Coords^[i] >= Bounds^[i].LowBound + Bounds^[i].ElementCount then
>     begin
>       result:=true;
>       break;
>     end;
> end;

Or, better yet

var
   i : sizeint;
begin
   Result:=false;
   I:=0;
   While (Not Result) and (I<=Pred(Dims)) do
     begin
     Result:= Coords^[i] >= Bounds^[i].LowBound + Bounds^[i].ElementCount;
     Inc(I);
     end;
end;

People really don't seem to get booleans, and why they scorn "While" is beyond me. All these ugly "break" statements :(

You may optimize even more by calculating Max:=pred(dims) once and doing I<=Max;

Michael.