Re: GH replacement proposal (includes a bit of Unicode)

[Marius Vollmer <mvo@zagadka.de>]

Dirk Herrmann <dirk@dirk-herrmanns-seiten.de> writes:

> Marius Vollmer wrote:
>
>>  Dirk Herrmann <dirk@dirk-herrmanns-seiten.de> writes:
>>
>> > Marius Vollmer wrote:
>> >
>> >> Hmm, yes, that might make sense. However, the -1 idiom is pretty
>> >> much standard for this kind of interface, no?
>> >
>> > I personally don't like this kind of 'one value, several meanings'
>> > paradigm:
>> >
>> > - What, if instead of -1, you pass -2? [...] - Readability suffers.
>> > [...]
>>
>>  Yes, I agree that the -1 idiom is not self explaining, but it is well
>>  established and people will instantly recognize it. I'd even argue
>>
> What about the -2 and so on?

The way it is worded in the proposal right now, -2 would be
interpreted as an unsigned value, that is, as a very large length.  In
other words, only one value, ((size_t)-1), is interpreted specially.

> You are trying to explain why the -1 idiom is not too bad.

I'm arguing that it is well known, not that it is necessarily good or
better.  Also, I really do think that people expect to be able to pass
-1 as the length parameter, as a convenience feature.

One point of the proposal is to make the API very easy to use, where
the 'obvious' way to use it is also the correct one.

So, IMO, we need to interpret -1 specially.  The question is then, is
it an advantage to have an additional way to have Guile count the
string length on its own?

> But, why do you think it is better?

I think it is good enough, but I'm of course listening to your
arguments.

>>  established and people will instantly recognize it. I'd even argue
>>  that they will expect to be able to pass -1 for a 'len' parameter and
>>  will be annoyed when they find out that Guile doesn't allow it.
>
> That's a guess. Maybe you should ask the people what they would prefer?
> Considering me as part of them, I would not prefer having the -1 idiom.

Noted.

> Summarized, I would just claim that it is not a good API design,
> since I have not yet seen a convincing argument in favor of it.

Yeah, I'm convinced.

> Considering your and Paul's answer, I would like to change my suggestion
> to the following pair of functions:
>
> SCM scm_from_locale_string (const unsigned char *str, size_t len);
> SCM scm_from_locale_0string (const unsigned char *str);

I would not like to use the "memory" term to indicate a string that is
not zero terminated; "memory" is too generic.  Also, "0string" feels
not right either, since it makes it look as if a 0string would
be something very special although it is the ordinary thing (for C).

What about

   SCM scm_from_locale_string (unsigned char *str);
   SCM scm_from_locale_string_counted (unsigned char *str, size_t len);

'scm_from_locale_string_counted' would treat len == -1 specially.

-- 
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