Re: Creates pure closures (issue 4894052)

[n . puttock]

Hi Mike,

I have reservations about the naming, since you're basically creating a
smob which acts as a container for a pair of callbacks; it doesn't work
like a simple-closure in that you can evaluate the closure and get
something useful back.

Cheers,
Neil


http://codereview.appspot.com/4894052/diff/1/lily/pure-closure.cc
File lily/pure-closure.cc (right):

http://codereview.appspot.com/4894052/diff/1/lily/pure-closure.cc#newcode65
lily/pure-closure.cc:65: 2, 0, 0, (SCM pc),
1, 0, 0,

(there's only one arg; looks like you've been cut'n'pasting from
simple-closure.cc :)

http://codereview.appspot.com/4894052/diff/1/lily/pure-closure.cc#newcode73
lily/pure-closure.cc:73: 2, 0, 0, (SCM pc),
1, 0, 0,

http://codereview.appspot.com/4894052/diff/1/lily/pure-closure.cc#newcode84
lily/pure-closure.cc:84: scm_display (scm_cdr (s), port);
this only displays the unpure part, and if you change it to show both,
there seems to be a garbage collection problem (probably to do with
using scm_markcdr in init_pure_closure ()); the pure part has been swept
away:

\relative c' {
  \override Stem #'Y-extent =
    #(ly:make-pure-closure ly:stem::height '(-3 . 10))
  c4
}

\layout {
  \context {
    \Voice
    \override Stem #'after-line-breaking =
    #(lambda (grob)
       (let ((data (ly:grob-property-data grob 'Y-extent)))
         (and (ly:pure-closure? data)
              (newline)
              (display data))))
  }
}

-> #<pure-closure #<primitive-procedure ly:stem::height> #<freed cell
0x7f4148a3f960; GC missed a reference> >

(the wrapper you posted fails even for a \once \override, and would be
bad for documentation purposes since the pure part would show as an
anonymous lambda)

http://codereview.appspot.com/4894052/