Re: Avoiding side effects

[Anders Wirzenius <anders@no.email.thanks.invalid>]

Jean-Pierre Rosen <rosen@adalog.fr> writes:

> Anders Wirzenius a �crit :
> > Please don't feel like I am provocative. I just want to find out
> > the difference between exceptions and side effects:
> > Why is an exception in this case not considered to be a side
> > effect?
> >
> To me, an exception is more like a kind of result rather than a side-effect.
> 
> A subprogram is intended to provide a certain service; either it can
> provide the intended result, or it must tell the caller, in an
> unambiguous way, that the correct result could not be provided; that's
> what exceptions are for.
> 
> If you compare exception with a return code, the difference is that
> you can easily ignore a return code, but not an exception. And
> remember:
>     "There is only one thing worse than a program that crashes:
>      a program that gives wrong, but likely results."

Thanks for this excellent clarification. Actually there exists
already occurrences of an exception in both functions. To
"translate" those Ada.Text_IO.End_Of_File (...) occurrences to a
global EOF_variable is just clumsy. Much better to use the
exceptions directly in the main program.

Thanks for your time.

-- 
Anders