Re: [Gm2] ISO exceptions source

[Gaius Mulley]

Martin Kalbfuß <address@hidden> writes:

> Hi,
>
> I try to use exceptions.
>
> I do for example:
>
> PROCEDURE VectorAddition(Vector1, Vector2 : ARRAY OF REAL;
>                          VAR Result       : ARRAY OF REAL);
> VAR
>       Index  : CARDINAL;
>       Source : EXCEPTIONS.ExceptionSource;
> BEGIN
>       IF HIGH(Vector1) <> HIGH(Vector2) THEN
>          EXCEPTIONS.AllocateSource(Source);
>          EXCEPTIONS.RAISE(Source, 1, 'Error: Vectors of different size');
>       END;
>       FOR Index := 0 TO HIGH(Vector1) DO
>           Result[Index] := Vector1[Index] + Vector2[Index];
>       END;
> END VectorAddition;
>
>
> Is there anything I should do with the Source? Or should I only allocate
> it?

Hi Martin,

your code above would raise and exception appropriately - however if
you had multiple modules many of which could raise an exception you
wouldn't know which exception had been raised.

So I would perform the AllocateSource in the initialisation section of
the module and then provide another procedure function to test whether
the exception raised came from Source.  Ie:


PROCEDURE VectorAddition(Vector1, Vector2 : ARRAY OF REAL;
                          VAR Result       : ARRAY OF REAL);
VAR
        Index  : CARDINAL;
        Source : EXCEPTIONS.ExceptionSource;
BEGIN
        IF HIGH(Vector1) <> HIGH(Vector2) THEN
           EXCEPTIONS.RAISE(Source, 1, 'Error: Vectors of different size');
        END;
        FOR Index := 0 TO HIGH(Vector1) DO
            Result[Index] := Vector1[Index] + Vector2[Index];
        END;
END VectorAddition;


PROCEDURE IsMyException () : BOOLEAN ;
  (* Returns TRUE if the current coroutine is in the exceptional
     execution state because of the raising of an exception from
     Source; otherwise returns FALSE.
  *)
BEGIN
   RETURN( IsExceptionalExecution() AND IsCurrentSource(Source) )
END IsMyException ;


BEGIN
   EXCEPTIONS.AllocateSource(Source);
END ...


have a look at gm2/gm2-libs-iso/IOChan.mod or
gm2/gm2-libs-iso/WholeConv.mod for some more ideas,

regards,
Gaius