Re: Bug with extended type?

// try treating the number as string;
class function TmxcUtil.ConvertVersionAsString(AMajorVersion, 
AMinorVersion: Integer) : Extended;
begin
  Result := intToStr ( AMajorVersion ) + '.' + inttoStr ( AMinorVersion );
end;

if ConvertVersionAsString(1, 20) >= '1.20' then
  ShowMessage ( 'YOU''LL GET HERE' );

// Best regards,
// Felipe

  ----- Original Message ----- 
  From: michael_grimard 
  To: [email protected] 
  Sent: Thursday, July 31, 2003 6:25 PM
  Subject: [Delphi] Bug with extended type?


  Hi,
    I have a function in a shared utility that I use to convert the 
  major version and minor version to an extended type.

  class function TmxcUtil.ConvertVersionAsExtended(AMajorVersion, 
  AMinorVersion: Integer) : Extended;
  begin
    Result := AMajorVersion + AMinorVersion/100
  end;

  If I call with ConvertVersionAsExtended(1, 20), it should return me 
  with 1.2.

  The version controls what the program can read from a file. The file 
  can change between versions, so I need to check its version to know 
  what I can read.

  The problem is that the comparison doesn't always work...

  if ConvertVersionAsExtended(1, 20) >= 1.20 then
    Read;  // <-- I don't go here!!!

  I am suprised that ConvertVersionAsExtended(1, 20) returns 
  1.19999999999999996 instead of 1.2, since it can (assign 1.2 in an 
  extended variable and check with the debugger, you will see that the 
  value of the variable is still 1.2).

  I made a sample test project that called my function with the same 
  parameter and that time, ConvertVersionAsExtended(1, 20) returns 1.2 
  as I expected it.

  How can that happened?

  I check the generated code with the debugger and the code generated 
  for the same function in my two projects is different.

  So, my guess is that with my real project, the compiler doesn't use 
  and extended type as supposed, but it uses a double instead, but in 
  my test project, the compiler make the computation with extended 
  variables.

  To prove that, I put the result returned by ConvertVersionAsExtended
  (1, 20) in a variable of type double and the variable is equal to 
  1.19999999999999996. So the extended variable that is returned by my 
  function, in fact has the precision of a double?!?

  I placed all my variables in my function in new variables of 
  extended type before doing the computation and the result is still 
  the same...

  Anyone has ever seen something like this?

  I'm using Delphi 5 Pro.

  Thanks,
  Michael



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