Re: Making a list argument reliably optional

[Robin Bannister]

David Kastrup wrote:


> A number list counts as not-number?.  

So I changed the not- number? predicate to also exclude number-list? but 
this was no better.  And then I determined all the individually 
problematic lilypond-scheme-predicates and also excluded these in the 
predicate never-matches-a-number? - which nevertheless matched a number.

That was when I gave up fighting the automagic.



> So if you are out for a more specific type of list before a number,
> you should check for that.

I was using what might be described as a sparse ordered list, basically 
markup-list? but having its gaps filled with rogue elements, for which I 
used a (non-markup) asterisk.
Following your advice, I got this working in stellated_ok.ly.

But this seemed overly complicated:
 - the predicate definition had to be separate (AFAICS)
 - the list had to be set up in Scheme.

That was when I decided to embrace automagic.
The rogue elements are now markup too, matched with the help of 
markup->string:
 - the predicate is just markup-list?
 - the list can be set up with \markuplist.
The in-band key is unlikely to be a problem.



Thanks for your help.

Cheers,
Robin

stellated_ok.ly
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