Hello Pedro,
Am 04.12.18 um 04:28 schrieb Pedro Pessoa:
> Hello!
> I want a function that takes a string as arg an from that produces a valid
> variable reference, as follows:
>
> %%% pseudo
> Nabc={a1 d e f}
> Nxyz={b1 e a d}
>
> fun=
> #(define-music-function (x)(string?)
> #{
> <<
> #(concat x "abc")
> \\
> #(concat x "xyz")
> >>
> #})
>
> \fun "N" %produces parallel music with Nabc and Nxyz
> %%%
>
> ---
>
> I've ran this test:
>
> %%%
> \Nabc={some music}
> (display (string->symbol (string-append "N" "abc")))
> %%%
>
> It outputs "Nabc", not the music content of Nabc, as I expected.
> Why is that? How do I make it point to the actual music?
The string is converted to a symbol and a symbol is a primitive datatype
in guile-scheme. To receive the value of the variable you have to ask
the parser. To place the result in the music you should use an instant
scheme expression (introduced by '$' not '#').
HTH:
fun=
#(define-music-function (x)(string?)
#{
<<
$(ly:parser-lookup (string->symbol (string-append x "abc")))
\\
$(ly:parser-lookup (string->symbol (string-append x "xyz")))
>>
#})
Jan-Peter
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