Re: String filtering

["Steve Whalen" <SteveWhalen001@hotmail.com>]

Robert A Duff wrote:

> ... Ada allows side effects in functions.   ...

...

[Good examples of idioms where permitting "out" parameters in functions
would aid clarity of Ada code snipped out]

[examples included recursive descent parsers, "get token" or "get line"
type functions, and function parameter initializations]

...

Thanks for the explanation.

You've sold me. I was leaning toward Tucker's position that "out"
parameters had no place in Ada, but now I think they probably should be
allowed (especially since the other kinds of side effects functions are
allowed to have are probably generally worse and have to found using
other tools or code inspections anyway).

If I'm managing a project and want to see where programmers used "out"
parameters in functions (if they were allowed), I could run an ASIS
based tool to find them and review them to be sure the programmer was
making sensible use of the (proposed) feature (as in your examples) and
not getting "cute".

...

> - Bob
>
> P.S. "Side effect" is a pejorative term.  (Some drug cures your disease,
> but makes you nauseous.)  If the effect is intended by the programmer,
> and clear in the code, perhaps we should call it an "effect", without
> the "side".

You're right. I guess "side effect" as I was using it is really a
contraction of "unintended side effect" which is a bad thing, but as
you point out, not all side effects are bad or unintended.  And since
the language doesn't prevent ALL side effects for functions,
eliminating the "out" parameters adds limitations that really don't add
much counterbalancing safety.

Steve