Re: pure simple-closures

[Han-Wen Nienhuys]

Joe Neeman schreef:

> Mostly because at the time that I wrote it, I couldn't figure out how to
> handle arbitrary length argument lists in scheme (the only way I
> currently know is to build the list of arguments, cons in the function

I think you're looking for the apply function,

  (apply func arg-list)

> > > 2) adopt the convention that if any argument in a simple-closure is
> > > UNDEFINED, the entire closure is UNDEFINED. This allows us to abort the
> > > evaluation of a pure closure when there is an unpure function with no
> > > pure equivalent. This requires changing the SCM_UNDEFINED in
> > > grob-closure.cc to scm_from_int(0).
> > Isn't there another value you could use for that?
> >
> > SCM_UNDEFINED is also used for callbacks with optional arguments (grep 
> > for OPTARGS).
>
> It seems that in every OPTARGS callback, the optional argument defaults
> to zero. The only difference in changing grob-closure.cc is that
> outside_slur_callback will now return zero instead of SCM_UNDEFINED in a
> few cases. But then Grob::get_offset will interpret the SCM_UNDEFINED as
> zero anyway.
>
> In the context of [XY]-offset, a non-procedure, non-number value is
> interpreted as zero. So I don't think there is any confusion in
> interpreting them as zero in chain_offset_callback.

OK; Just make sure that we can still chain procedures with non-number 
return values.

--

Han-Wen Nienhuys - address@hidden - http://www.xs4all.nl/~hanwen

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