Hi Paul!
Paul Smith <psm...@gnu.org> skribis:
> On Sun, 2011-09-18 at 14:10 +0200, Ludovic Courts wrote:
>> There are two problems I can think of here:
>>
>> - string unquoting is actually more complex than this (recall that
>> ‘object->string’ merely calls ‘write’):
>> - ‘scm_c_eval_string’ can return any Scheme objects, some of which
>> have meaningless representations as strings:
>>
>> The latter is probably the most serious question. I think you would
>> really want to constrain expressions passed in $(guile ...) to return
>> a string, and not any other type of objects.
>>
>> In that case, you could solve the first problem by using (display ...)
>> instead of (write ...).
>
> There's no question that the string conversion is a hack: that's mainly
> why I'm asking here :-).
Heh, understood. :-)
> I don't want to restrict it to just strings; for example I'd have to
> support numbers as well (one of GNU make's main issues right now is that
> there is no math capability whatsoever). I'd like to be able to
> possibly convert other things like t and nil (in GNU make's terms,
> "false" is the empty string and "true" is any non-empty string). Maybe
> there are other things as well (what about symbols like 'foobar?), I
> don't know.
OK, makes sense. What about defining the Scheme data types that would
be acceptable to pass back at the make level? I think you pretty much
listed them above: strings, numbers, and booleans.
In your code, you would type-check them along these lines:
char *c str;
[...]
if (scm_is_string (obj))
c_str = scm_to_locale_string (obj); /* No quoting issue here. */
else if (scm_is_number (obj))
c_str = scm_to_locale_string (object_to_string (obj));
else if (scm_is_false (obj))
c_str = strdup ("#f");
else if (scm_is_eq (obj, SCM_BOOL_T))
c_str = strdup ("#t");
else
scm_wrong_type_arg (__func__, 0, obj);
> As above, the double-quote stripping is intensely hacky :-). I'll look
> into the concepts of display and write and see what I can figure out.
> Any suggestions or pointers to example code are welcome.
See info "(guile) Scheme Write".
Thanks,
Ludo’.
