Re: use variable in \markup \override

[Mark Knoop]

At 16:03 on 16 Oct 2013, David Kastrup wrote:
>Mark Knoop <address@hidden> writes:
>
>> Is there any way to use a variable in a \markup \override?
>
>That has nothing to do with LilyPond, but rather with Scheme.
>
>> gap = 5
>> bskip = #'(baseline-skip . 5)
>
>' means: don't evaluate the following expression.  When expressions are
>evaluated, lists and symbols are converted into function calls and
>variable references, respectively.
>
>An override always consists of a symbol and a value.  5 is a
>"self-evaluating constant": there is no difference between '5 and 5 at
>all.
>
>>
>> \markup {
>>   \override #bskip                   % <--- this does work
>>   %\override #'(baseline-skip . gap) % <--- this does not work
>
>The easiest way is to use a backquoted list here:
>
>\override #`(baseline-skip . ,gap)
>
>When you backquote a list, it is quoted as usual _except_ that any
>comma expression inside _does_ get evaluated.  Which in this case means
>replacing the _symbol_ gap with the value in the _variable_ named gap.
>
>You can also cobble together your (dotted) list manually:
>
>\override #(cons 'baseline-skip gap)
>
>Note that cons is a function for making a "dotted pair".  We need to
>quote the symbol baseline-skip to keep Scheme from trying to look at
>the value of a variable called baseline-skip.  We don't quote gap
>since here we _do_ want the variable value instead of a symbol gap.

Thank you David.

-- 
Mark Knoop