On 2013/10/07 14:10:09, dak wrote:
On 2013/10/06 01:15:12, david.nalesnik wrote:
> There is a major problem with this patch set which I don't know how
to
address.
>
> The examples below represent my efforts to test the effects of
multiple
> applications of \offset. You can see that some accumulation is
possible.
> However, the last two examples (commented out) will cause a crash.
All I can
> think of is that this relates to the multiple instances of "self" in
the
> properties alist. I've verified that the instances aren't identical
despite
> having the same name, so I don't understand why there should be a
problem.
I suppose the problem is with
+(define (find-value-to-offset prop self alist)
+ "Return the first value of the property @var{prop} in the property
alist @var
+that is not @var{self}."
+ (let loop ((ls alist))
+ (if (null? ls)
+ #f
+ (if (eq? prop (car (first ls)))
+ (if (eq? self (cdr (first ls)))
+ (loop (cdr ls))
+ (cdr (first ls)))
+ (loop (cdr ls))))))
First: try using GUILE srfi-1 functions for that kind of thing: they
are more
readable than explicit loops.
I've used member, and I've also incorporated Lily's assoc-get.
But what you need here is "return the first value of the property
@var{prop} in
the property
alist @var{alist} @em{after} having found @var{self}."
You _always_ have to _first_ pass self before looking for anything
else. If you
find a valid property _before_ finding self, ignore it and continue
looking.
Otherwise you end up in a mutual recursion.
Changes made--works like a charm! There are now more possibilities for
accumulation. Possibly another regtest `offset-accumulation.ly' is
warranted? (As far as documenting the abilities for accumulation: this
may be more confusing than worthwhile.)
If you don't find self at all, its head-scratching time: after all,
who called
you then? I lean toward throwing an error: continuation strategies
might be
fragile.
Well, if self isn't found, then we're dealing with a tweak, which
wouldn't have added to the alist. In that case, the function
`find-value-to-offset' as rewritten will simply return the first
instance of the property in the alist. `offsetter' should catch
situations where the user tries to offset something not in the basic
properties alist.
https://codereview.appspot.com/8647044/
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