[gsharp-devel] key signatures

[Christophe Rhodes]

Christophe Rhodes <csr21 at cam.ac.uk> writes:

> I'm attaching my current diff, which covers all but two cases, I
> believe.  The two remaining pieces are

Exactly the same caveats as in my previous message still apply.  I
attach my current patch, updated for the weekend's rearrangements (now
using INVALIDATE-SLICE-USING-STAFF in the relevant places).  Sorry I'm
not being terribly good at actually finishing the remaining
functionality...

What I basically need is, I think, to be able to treat a staff as a
temporally-ordered sequence of elements, irrespective of which layer
they come from; then I can use analogues of CL's sequence functions
(e.g. FIND-IF #'KEY-SIGNATURE-P <seq> :end <pos> :from-end t) to find
the applicable key signature for a given element.  I'm not certain
that this is the right interface, of course: it looks a bit like it
could lead to O(n^2) behaviour quite easily; I think this could be
mitigated by having the sequence for a staff's elements be a
flexirank, because I already keep a cache of a staff's key signatures
in a slot in that staff, so searching for key signatures (and deciding
whether an element is after a key signature or not) would be a simple
comparison of ranks.

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Cheers,

Christophe