msk...@ansuz.sooke.bc.ca writes: > On Sun, 2 Dec 2018, David Sumbler wrote: >> > But MusiXTeX can do "if" statements. > >> I felt that an "if" would be useful, so I eventually came up with: > > That is useful for conditional includes, but it can't be embedded in the > data structure that LilyPond calls "music" and stores in variables. As > soon as something is turned into "music" it has to be data, not code; > conditionals must either be evaluated before the input is turned into > "music," or by separate code (usually, in Scheme rather than in LilyPond > as such) that conditionally modifies the static "music." That latter > approach, with tags in the "music" that can be filtered out, is what's > usually recommended as a substitute for real conditionals in LilyPond, but > it's quite limiting compared to what programming languages can do with > "if." > > For those familiar with programming languages it's not so mysterious why > this situation comes about. LilyPond takes care to call its variables > variables in the documentation. You reference them; you don't execute > them. They contain data, not code. Obviously, data will be the same > every time you look at it, unless you externally change it. But I wish > that without escaping to Scheme I could have something more like a macro > than like a variable, evaluating its conditionals (and doing other > programming-language stuff) every time it is used.
Have you looked at tags? -- David Kastrup _______________________________________________ lilypond-user mailing list lilypond-user@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-user
