Simon Albrecht <simon.albre...@mail.de> writes: > On 04.11.2015 20:36, David Kastrup wrote: >> Simon Albrecht <simon.albre...@mail.de> writes: >> >>> On 04.11.2015 19:24, David Kastrup wrote: >>>> Simon Albrecht <simon.albre...@mail.de> writes: >>>> >>>>> This compiles fine inasmuch as the output is just as intended, but it >>>>> does sport a: >>>>> >>>>> <0>"/home/simon/lilypond/tests/wrap-multiple-books.ly:17:1: error: bad >>>>> expression type >>>>> >>>>> \printParts one.two" >>>>> >>>>> Is this worth a bug report about this error appearing too easily? >>>> No. You use map instead of for-each, >>> How would I use for-each here? I’m not familiar with that. >> for-each has exactly the same arguments as map but does not return a >> value. >> >>>> you use define-scheme-function instead of define-void-function. >>> Ah, I see. I wouldn’t have thought that a function which basically >>> runs print-book-with-default would classify as a void function. >> What do you consider "void" then? > > Basically, my notion of a ‘void function’ comes from the LilyPond > documentation, and I’d phrase it as ‘a function which is not executed > for its output (or return value), but for side-effects’, such as > variable definitions &c. > And I thought print-book-with-default was executed in order to output > a ‘book’.
Which is not a return value. Consequently a side-effect. > Is it closer to the truth to say that it only passes the information > on, instead of ‘returning’ or ‘outputting’ it? Any effect apart from returning a value is a side-effect. This includes writing to files and variables out of a function's scope. It also includes reading from files if that read causes any change like an advancement of a file pointer. -- David Kastrup _______________________________________________ lilypond-user mailing list lilypond-user@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-user
