Re: [PATCH v1 02/36] Guile extension language: doc additions

[Doug Evans <xdje42@gmail.com>]

On Sat, Jan 18, 2014 at 12:42 PM, Ludovic Courtès <ludo@gnu.org> wrote:
> Doug Evans <xdje42@gmail.com> skribis:
>
>> On Fri, Jan 3, 2014 at 1:30 PM, Ludovic Courtès <ludo@gnu.org> wrote:
>>>>> +The optional @var{errors} argument is either @code{"strict"}
>>>>> +or @code{"replace"}.  A value of @code{"strict"} corresponds to
>>>>> +Guile's @code{SCM_FAILED_CONVERSION_ERROR} and a value of @code{"replace"}
>>>>> +corresponds to Guile's @code{SCM_FAILED_CONVERSION_QUESTION_MARK}.
>>>>
>>>> Suggest a cross-reference to Guile documentation here.
>>>
>>> Agreed.  Also, Guile talks of “conversion strategy” and “conversion
>>> error handler”, with values ‘error’, ‘substitute’, and ‘escape’ (at the
>>> Scheme level), and I’d recommend sticking to those names and terminology.
>>
>> The values chosen were to be consistent with the python support.
>> OTOH I *do* like being more consistent with the particular extension
>> language at hand.
>> I've tentatively changes things to use "error" and "substitute".
>> Question: How about exporting the SCM_FAILED_CONVERSION_* constants
>> and using those instead?
>>
>> E.g, (value->string foo #:errors SCM_FAILED_CONVERSION_ERROR) ?
>
> I’d rather use a symbol:

Yeah, I thought of that, but the encoding is a string,
so it'd be "#:encoding string #:errors symbol".

I don't have a strong preference, but using a symbol here while
feeling Schemey feels too weird.
It's not a strong preference though.
[I do have a strong preference that the encoding not be a symbol, not
all encodings could be valid Scheme symbols.
OTOH, support could be added for both strings and symbols for both
#:encoding and #:errors in a later patch if a compelling case for it
was presented.]

>   (value->string foo #:conversion-strategy 'error)
>
> So that has to be converted in C but I think that’s OK.

#:conversion-strategy is more to type than #:errors but I'm happy to
change it if you want.
Though this is a case where I would not want to support both
#:conversion-strategy and #:errors so whatever we pick is it.

We can create a 'error symbol at start up and just use scm_eq so the
comparison is easy enough.

> (I just noticed that Guile’s ‘pointer->string’, which is similar, lacks
> this argument.)