Delphi Sorting TListView Question - delphi

Question

I'm using the code from: http://www.swissdelphicenter.ch/torry/showcode.php?id=1103
to sort my TListView, which works GREAT on everything but numbers with decimals.
So I tried to do this myself, and I created a new Custom Sort called: cssFloat
Created a new function
function CompareFloat(AInt1, AInt2: extended): Integer;
begin
if AInt1 > AInt2 then Result := 1
else
if AInt1 = AInt2 then Result := 0
else
Result := -1;
end;
Added of the case statement telling it what type the column is..
cssFloat : begin
Result := CompareFloat(i2, i1);
end;
And I changed the Column click event to have the right type selected for the column.
case column.Index of
0: LvSortStyle := cssNumeric;
1: LvSortStyle := cssFloat;
2: LvSortStyle := cssAlphaNum;
else LvSortStyle := cssNumeric;
And The ListView Sort type is currently set to stBoth.
It doesn't sort correctly. And Ideas on how to fix this?
Thank you
-Brad

Answer 1

I fixed it... after 3 hours of struggling with this.. not understanding why.. I finally saw the light.. CompareFloat was asking if two integers were greater or less than each other.
cssFloat : begin
r1 := IsValidFloat(s1, e1);
r2 := IsValidFloat(s2, e2);
Result := ord(r1 or r2);
if Result <> 0 then
Result := CompareFloat(e2, e1);
end;
(Copied and modified from EFG's Delphi site)
FUNCTION isValidFloat(CONST s: STRING; var e:extended): BOOLEAN;
BEGIN
RESULT := TRUE;
TRY
e:= StrToFloat(s)
EXCEPT
ON EConvertError DO begin e:=0; RESULT := FALSE; end;
END
END {isValidFloat};

Answer 2

While I don't know what is the problem which you faced perhaps is useful for you...
function CompareFloat(AStr1, AStr2: string): Integer;
const
_MAGIC = -1; //or ANY number IMPOSSIBLE to reach
var
nInt1, nInt2: extended;
begin
nInt1:=StrToFloatDef(AStr1, _MAGIC);
nInt2:=StrToFloatDef(AStr2, _MAGIC);
if nInt1 > nInt2 then Result := 1
else
if nInt1 = nInt2 then Result := 0
else
Result := -1;
end;
..and another snippet (perhaps much better):
function CompareFloat(aInt1, aInt2: extended): integer;
begin
Result:=CompareValue(aInt1, aInt2); // :-) (see the Math unit) - also you can add a tolerance here (see the 'Epsilon' parameter)
end;
Besides the rounding which can cause you problems you can see what the format settings are in conversion between string and numbers (you know, the Decimal Point, Thousands Separator aso.) - see TFormatSettings structure in StringToFloat functions. (There are two - overloaded).
HTH,