Re: pure simple-closures

[Han-Wen Nienhuys]

Joe Neeman schreef:
> Here is an attempt at making simple-closures pure-evaluatable. A
> summary:
>
> 1) move the conversion of non-pure-to-pure callbacks into C++ where it
> is a bit easier to access and generalise it to support functions other
> than just grob callbacks. The convention is that if a non-pure function

I'm not sure about this ; why not in Scheme?  (In general, we've had a 
movement of stuff out of C++, not back to C++).

> takes (arg1 arg2 arg3) as arguments then the pure version will take
> (arg1 start end arg2 arg3) as arguments. This order is so that we can
> have arg3, for example, as an optional argument.


> 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).

> I haven't actually written any new pure functions yet, so the impact is
> fairly small. I'll try to do a pure_avoid_slur_callback before 2.10. I
> should point out, though, that the main problem in issue #113 has been
> mitigated somewhat by the fact that TextScripts usually use normal
> procedures now for Y-offset.


--

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

LilyPond Software Design
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