Hello Lukas, Many thanks for the clarification. My apologies for the belated reply since my week got quite busy. I understand your explanation: You can also use the question mark in the variable name, which confused me for a moment.
I think I was mixing information I read previously about predicates in LilyPond, and thought myself restricted to the list here: http://lilypond.org/doc/v2.20/Documentation/notation/predefined-type-predicates I could also modify your to use a boolean explicitly: scoreIf = #(define-void-function (some-condition score) (boolean? ly:score?) (if some-condition (add-score score))) But I'm really no Scheme expert. Still hacking my way through. Many thanks, mattfong On Thu, Dec 3, 2020 at 8:45 AM Lukas-Fabian Moser <l...@gmx.de> wrote: > Hi Matthew, > > Am 03.12.20 um 01:50 schrieb Matthew Fong: > > ... and I will have use of question? Didn't know about that! > > In fact, that's just an arbitrary name for a variable! (And, to be > honest, I wasn't completely happy with my choice.) > > So, the following would work just the same: > > scoreIf = #(define-void-function (some-condition score) (scheme? ly:score?) > (if some-condition (add-score score))) > > I would have liked to use "condition" or "cond", but these are reserved > words in Guile, if I'm not mistaken. Maybe "print-it" would be a nice > name: "if print-it (add-score score)" seems to be quite self-explanatory. > > As for the ? in "question?": By convention, names ending in "?" are used > for "predicates", that is, functions returning only #t or #f as values. > I seem to remember that some people extend this convention and use the ? > also for variables that should contain boolean values (#t/#f), and > that's what I did here. > > Lukas > >
