From: Ray Blaak <rAYblaaK@STRIPCAPStelus.net>
Subject: Re: Naming convention to identify functions with side effects
Date: Tue, 30 Sep 2008 17:40:48 GMT
Date: 2008-09-30T17:40:48+00:00 [thread overview]
Message-ID: <ud4ilh6qx.fsf@STRIPCAPStelus.net> (raw)
In-Reply-To: 48e24307$0$6583$9b4e6d93@newsspool4.arcor-online.net
Georg Bauhaus <rm.dash-bauhaus@futureapps.de> writes:
> I need more predicates. Since these are called before Load_Web_Page
> is called, Load_Web_Page is "pushed down" the conditional chain,
> hiding it and also blurring the distinct sources of error:
>
> if URL_Name /= null and then
> Valid_Protocol (URL_Name.all) and then
> Host_Allowed (URL_Name.all) and then
> No_Up_Directories (URL_Name.all) and then
> Load_Web_Page (URL_Name.all)
> then ...
> [stuff to do if all test succeed and the page was finally loaded]
> else ...
> [something has failed, maybe loading has failed, do other stuff]
> end if;
[...]
> Finally, the programmer wanting to reduce verbosity by
> making Load_Web_Page a Boolean function now causes
> verbosity by chaining the many predicates.
> This amount by far exceeds the intended reduction in verbosity
> and renders the original intent (of saving words) mostly
> fruitless.
[...]
> At this point I remember advice from The Little Schemer
> to use little helper functions (that can be nested if
> needed). Thus,
>
> if Is_Acceptable (URL_Name.all) then
> Load_Web_Page (URL_Name.all, Data);
> Construct (Data, Result);
> else
> raise Syntax_Error;
> end if;
Or, you could make Load_Web_Page only work if a page is valid:
if Load_Web_Page (URL_Name.all, Data) then
Construct (Data, Result);
else
raise Syntax_Error;
end if;
Or, my favourite, make Load_Web_Page be a procedure that wants only valid
pages and have *it* throw any errors as needed:
Load_Web_Page (URL_Name.all, Data); -- raises Syntax_Error if bad
Construct (Data, Result);
--
Cheers, The Rhythm is around me,
The Rhythm has control.
Ray Blaak The Rhythm is inside me,
rAYblaaK@STRIPCAPStelus.net The Rhythm has my soul.
next prev parent reply other threads:[~2008-09-30 17:40 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-29 18:17 Naming convention to identify functions with side effects Hibou57 (Yannick Duchêne)
2008-09-29 18:45 ` Hibou57 (Yannick Duchêne)
2008-09-29 18:55 ` Adam Beneschan
2008-09-29 19:52 ` Dmitry A. Kazakov
2008-09-29 20:48 ` Georg Bauhaus
2008-09-29 21:10 ` Adam Beneschan
2008-09-30 15:17 ` Georg Bauhaus
2008-09-30 17:40 ` Ray Blaak [this message]
2008-10-02 12:33 ` Ole-Hjalmar Kristensen
2008-10-03 9:18 ` Georg Bauhaus
2008-10-06 7:24 ` Ole-Hjalmar Kristensen
2008-10-03 11:51 ` Brian Drummond
2008-10-03 12:28 ` Dmitry A. Kazakov
2008-10-04 12:30 ` Marco
2008-10-04 13:05 ` (see below)
2008-10-04 15:14 ` Gary Scott
2008-10-11 11:32 ` Marco
2008-10-11 14:57 ` Dmitry A. Kazakov
2008-10-11 16:05 ` (see below)
2008-10-11 17:49 ` Georg Bauhaus
2008-10-11 18:42 ` (see below)
2008-10-03 13:15 ` Jeffrey Creem
2008-09-29 20:57 ` Georg Bauhaus
2008-09-29 22:22 ` Dr. Adrian Wrigley
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