Hi,

In the math unit are the CompareValue functions only for signed integers. Why not for DWORD and QWORD?

I tested with the program below.

For DWord is works correctly, presumely because the int64 overload is used. For QWord without typecast the code doesn't compile, because the compile cannot choose the right overload. With typecasts it returns the wrong values.

The math unit also has these lines:
{ this causes more trouble than it solves
function Min(a, b: Cardinal): Cardinal;
function Max(a, b: Cardinal): Cardinal;
}
It doesn't tell what problems and why.

Vincent

===========================================
program Project1;
{$mode objfpc}{$H+}

uses
Classes, SysUtils, Math

   { add your units here };

var
   d1, d2: dword;
   q1, q2: qword;
begin
   d1 := $F0000000;
   d2 := 10;
   writeln('CompareValue (d1,d2): ', comparevalue(d1,d2));
   writeln('CompareValue (d2,d1): ', comparevalue(d2,d1));
   q1 := $F000000000000000;
   q2 := 10;
   writeln('CompareValue (q1,q2): ', comparevalue(int64(q1),int64(q2)));
   writeln('CompareValue (q2,q1): ', comparevalue(int64(q2),int64(q1)));
   readln;
end.

In the math unit are the CompareValue functions only for signed integers. Why not for DWORD and QWORD?

I guess, that it's Delphi mimicing implementation (because it is Delphi-like).

And it can be tricky to distinguish signed and unsigned expression values.

Like,

a: qword;
a-1 --- ??? (anyone may know for sure that a-1>0 and want to subtract one)

I guess it's something like that.

If you check <http://www.freepascal.org/mantis/view.php?id=8448> you can see this bug in action - the fpcadds and math unit provide signed and unsigned versions of CompareValue, but the correct one is not always chosen.

Colin

What a lousy compiler we use! ;-)

Do you have a testprogram, so I can make a fpc bug report?

Vincent

Quoting Vincent Snijders :

I think this is inherent in the language design, as it is too easy to convert between signed and unsigned integers. For example should the call:

CompareValue(0,0)

use the signed or unsigned version?

Colin

But in this particular case, I did not use constants, but variables of
the same type.

Vincent