Things which are extra

Here we give a list of things which are possible in Free Pascal, but which didn't exist in Turbo Pascal or Delphi.

1. There are more reserved words. (see appendix B for a list of all reserved words.)
2. Functions can also return complex types, such as records and arrays.
3. You can handle function results in the function itself, as a variable. Example

   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. To do a recursive call in this you must append () behind the function name:

   function a : longint;
   
   begin
      a:=12;
      { this is the recursive call }
      if a()>4 then
        begin
           {...}
        end;
   end;

4. There is partial support of Delphi constructs. (see the Programmer's guide for more information on this).
5. The exit call accepts a return value for functions.

   function a : longint;
   
   begin
      a:=12;
      if a>4 then
        begin
           exit(a*67); {function result upon exit is a*67 }
        end;
   end;

6. Free Pascal supports function overloading. That is, you can define many functions with the same name, but with different arguments. For example:

   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;