Delphi Compiler Directive to Evaluate Arguments in Reverse

Question

I was really impressed with this delphi two liner using the IFThen function from Math.pas. However, it evaluates the DB.ReturnFieldI first, which is unfortunate because I n

Answer 1

The calling convention affects the way they are evaluated.
There is not a compiler define to control this.

Pascal is the calling convention you would have to use to get this behavior.

Although I would personally never depend on this type of behavior.

The following example program demonstrates how this works.

program Project2;
{$APPTYPE CONSOLE}
uses SysUtils;

function ParamEvalTest(Param : Integer) : Integer;
begin
  writeln('Param' + IntToStr(Param) + ' Evaluated');
  result := Param;
end;

procedure TestStdCall(Param1,Param2 : Integer); stdCall;
begin
  Writeln('StdCall Complete');
end;

procedure TestPascal(Param1,Param2 : Integer); pascal;
begin
  Writeln('Pascal Complete');
end;

procedure TestCDecl(Param1,Param2 : Integer); cdecl;
begin
  Writeln('CDecl Complete');
end;

procedure TestSafecall(Param1,Param2 : Integer); safecall;
begin
  Writeln('SafeCall Complete');
end;

begin
  TestStdCall(ParamEvalTest(1),ParamEvalTest(2));
  TestPascal(ParamEvalTest(1),ParamEvalTest(2));
  TestCDecl(ParamEvalTest(1),ParamEvalTest(2));
  TestSafeCall(ParamEvalTest(1),ParamEvalTest(2));
  ReadLn;
end.

This would require you to write your own IfThen Functions.

If you really want this to be a one liner you really can do that in Delphi. I just think it looks ugly.

If (DB.First = 0) then result :=  DB.ReturnFieldI('awesomedata1') else result := 0;