Re: Scheme void function problems

[David Nalesnik]

Hi again,

On Wed, Mar 25, 2015 at 10:33 AM, David Nalesnik <address@hidden> wrote:

Hi Simon,

I can't judge whether this is getting closer to you want, but maybe my observations can help.

On Wed, Mar 25, 2015 at 9:17 AM, Simon Albrecht <address@hidden> wrote:

Hello,

I’m experimenting with an implementation of automatic tagline language selection and currently have two problems with the void function \language that I adapted from music-functions-init.ly:
– I can’t get the first, optional argument to work; it needs to be explicitly given or Lily will take the string as first argument – although it’s required to be a symbol.

I haven't succeeded in making this work with the optional argument in the first position.  I moved it last.   However, the last argument either must be specified with a symbol or with \default.  Otherwise, the following _expression_ will be taken as the argument and an error will be raised: in my rewrite that is '#(newline)'. 

How about this?  I'm viewing the first argument as a slot for either a symbol ('general and the like) or a string (the language name).  The last argument is optional.  I used the scheme? predicate to solve the lookahead problem.  Anything will be taken, and it's up to the function to reject anything that's not a string.  (Presumably, it's unlikely that you'd follow the music function with a string, but who knows...)

HTH,

David

 

tagline-d.ly
Description: Text Data