Or alternatively (if you only need basepitch, not different octaves) you may avoid parsing and directly pull the pitch from the pitch name mapping (less powerful, but less chaotic and safer):
#(assoc-get (string->symbol "c") pitchnames)
or even (to avoid problems when changing language) from a specific language
set:
#(assoc-get (string->symbol "c") (assoc-get 'nederlands language-pitch-names))
(if you need different octaves you might of course specify this one
separately).
Evaluating strings passed from outside is a very good opportunity to allow
injection of arbitrary code, as you can see here:
#(ly:parse-string-expression
(ly:parser-clone)
"#(system \"echo Doing evil stuff ...; killall lilypond\")")
Also this makes no guarantee on what type of thing you get back, it might not
be a pitch! "c4" will evaluate to music, "(" will evaluate to a post event.
Unexpected and malformatted stuff like "{" will result in an uncaught error.
Using
#(assoc-get (string->symbol "c") pitchnames)
on the other hand will guarantee that the result is either a pitch or #f if no
valid pitch string was given (which then gives you the possibility of either
falling back to a default / not applying certain things or to exit with an
informative message.
Cheers,
Valentin
Am Sonntag, 24. September 2023, 23:09:33 CEST schrieb Jean Abou Samra:
> Try
>
> (ly:parse-string-expression (ly:parser-clone) (getenv "FROM_KEY"))
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