Re: [PATCH] Fix the R6RS exact-integer-sqrt and import into core guile

[Detlev Zundel]

Hi Mark,

> Since you don't want to continue this discussion on a theoretical basis,
> can you please provide a concrete example of how the addition of
> scm_exact_integer_sqrt might be a maintenance burden in the future,
> given that our public C interface already consists of approximately 2K
> functions, including most (maybe all?) of the other numeric operators?

Ok, ok, I have to admit that my reply extended the context from the
specific question of exact-integer-sqrt to the more broader question of
"write Scheme rather than C".  As such most of what I wrote should be
read in that broader context.

> What I'm asking for is a specific example of how some future change in
> the internal workings of Guile's implementation might result in us
> saying "Damn, if only we hadn't exported those last few numerical
> operators, this would've been less of a pain!"

Returning to the question at hand, rather than publishing lots and lots
of C interfaces, I would much rather see generic approaches like what
Andy wrote in his reply:

> Nota bene: this doesn't have to make the lives of C users difficult!  On
> the contrary, we have to make it easy to invoke the Scheme API, and in
> this case to get some number of expected return values.  For example in
> this case, one could do a:
> 
>   scm_call_1_2v (scm_variable_ref (exact_integer_sqrt_var), n, &root, &rest);

This looks very nice and reduces lots of function calls to a more
generic interface that will be easier to maintain and is completely
orthogonal to what is done in scheme.

The opposite side of this coin - calling C from scheme - is nicely
demonstrated by the sqlite3 bindings that Andy come up with[1].  In
there, _everything_ is done in scheme.  Not a single line of C is
needed.  This is due to the genericity of 'pointer->procedure' plus
'dynamic-func'.

In my opinion it is a worthwhile goal to strive for such genericity also
in the C calling to Scheme domain.

Cheers
  Detlev

[1] https://gitorious.org/guile-sqlite3

-- 
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