Thomas Morley <thomasmorle...@gmail.com> writes:
> 2017-04-18 10:55 GMT+02:00 David Kastrup <d...@gnu.org>:
>> Thomas Morley <thomasmorle...@gmail.com> writes:
>>
>>> 2017-04-17 21:08 GMT+02:00 Roman Stawski <ro...@stawski.fr>:
>>>> Hello all
>>>>
>>>>
>>>> I'm coming across a problem with context definitions:
>>>>
>>>> \layout {
>>>> \context {
>>>> \name P
>>>> \alias Voice
>>>> }
>>>>
>>>> This blows up with the error
>>>>
>>>> Interpreting music...ERROR: In procedure symbol->string:
>>>> ERROR: Wrong type argument in position 1 (expecting symbol): ()
>>>> Exited with return code 1.
>>>>
>>>> If I comment out the '\accepts' compilation finishes, (but ignores the
>>>> context P obviously).
>>>
>>> From: NR 5.1.6 Defining new contexts
>>>
>>> "The mechanisms with which contexts communicate are established by declaring
>>> the context \type. Within a \layout block, most contexts will be of type
>>> Engraver_group.
>>> [...]
>>> Copying and modifying an existing context definition will also fill in
>>> the type."
>>>
>>>
>>> So (see comments):
>>>
>>>
>>> \layout {
>>> %% define "P" from scratch
>>> \context {
>>> \type "Engraver_group"
>>> \name P
>>> \alias Voice
>>> %% put in engravers for what you want
>>> %% otherwise no output
>>> }
>>
>> Trigger and wording of error message are not overly helpful here. This
>> should likely be caught at an earlier point of time.
>>
>> --
>> David Kastrup
>
> Out of curiosity, could you point me to where the current error is triggered?
>
> I've added some debugging code:
>
> (define (print-book-with parser book process-procedure)
> (let* ((paper (ly:parser-lookup parser '$defaultpaper))
> (layout (ly:parser-lookup parser '$defaultlayout))
> (outfile-name (get-outfile-name parser book)))
>
> (pretty-print
> (list
> book
> paper
> (map
> (lambda (sym)
> (cons
> (ly:context-def-lookup
> (assoc-get 'P (ly:module->alist
> (ly:output-def-scope layout)))
> sym)
> sym))
> (list
> 'default-child
> 'consists
> 'description
> 'aliases
> 'accepts
> 'property-ops
> 'context-name
> 'group-type))
> (assoc-get 'P (ly:module->alist (ly:output-def-scope layout)))
> outfile-name))
>
> (process-procedure
> book
> paper
> layout
> outfile-name)))
>
> returning:
>
> (#<Book>
> #< Output_def>
> ((() . default-child)
> (() . consists)
> (() . description)
> ((Voice) . aliases)
> (() . accepts)
> (() . property-ops)
> (P . context-name)
> (() . group-type))
> #<Context_def P atest-55.ly:636:5>
> "atest-55")
>
> Though, I don't see symbol->string applied anywhere there.
My guess is lily/context.cc:
void
Context::create_context_from_event (SCM sev)
{
Stream_event *ev = unsmob<Stream_event> (sev);
string id = ly_scm2string (ev->get_property ("id"));
SCM ops = ev->get_property ("ops");
SCM type_scm = ev->get_property ("type");
string type = ly_symbol2string (type_scm);
It's probably the last line quoted that gives this error. The "accepts"
stuff is likely a red herring: if a context is not acceptable, it won't
get created in the first place and thus not trigger the error.
--
David Kastrup
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