Re: Problems with 'class, help anyone?

["Alexandre E. Kopilovitch" <aek@vib.usr.pu.ru>]

Robert A Duff (bobduff@shell01.TheWorld.com) wrote:
>"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
[skip]
>> just allow procedures with results:
>>
>>    procedure Foo (...) return Bar;
>
>Yeah, and then eliminate the "function Foo..." syntax.
>That would solve the problem!
>
>Slight incompatibility...  ;-)

There is another way, with perhaps even less incompatibility: let's introduce
third mode for a formal parameter - "return" mode (in addition to conventional
"in" and "out"). That "return" may be applied to the procedure's first parameter
only, and it means the same as "out" mode, with single exception: if the first
parameter of a procedure is in "return" mode then the procedure *may* be called
without the corresponding (first) argument, and in such a case it returns value.
For example:

procedure Two_Fold(Result : return Boolean; Something : in Integer);

X : Boolean;
Two_Fold(X, 0);  -- "return" as "out", procedure does not return value

if Two_Fold(0) then  -- first argument omitted, procedure returns value
  ...
end if;



Alexander Kopilovitch                      aek@vib.usr.pu.ru
Saint-Petersburg
Russia