Here we give a list of things which are possible in Free Pascal, but which didn’t exist in Turbo Pascal or Delphi.
function a : longint; begin a:=12; while a>4 do begin {...} end; end;
The example above would work with TP, but the compiler would assume that the a>4 is a recursive call. If a recursive call is actually what is desired, you must append () after the function name:
function a : longint; begin a:=12; { this is the recursive call } if a()>4 then begin {...} end; end;
function a : longint; begin a:=12; if a>4 then begin exit(a*67); {function result upon exit is a*67 } end; end;
procedure DoSomething (a : longint); begin {...} end; procedure DoSomething (a : real); begin {...} end;
You can then call procedure DoSomething with an argument of type Longint or
Real.
This feature has the consequence that a previously declared function must always be defined
with the header completely the same:
procedure x (v : longint); forward; {...} procedure x;{ This will overload the previously declared x} begin {...} end;
This construction will generate a compiler error, because the compiler didn’t find a definition of procedure x (v : longint);. Instead you should define your procedure x as:
procedure x (v : longint); { This correctly defines the previously declared x} begin {...} end;
The command line option -So (see page 135) disables overloading. When you use it, the above will compile, as in Turbo Pascal.