Re: define-void-function

[Freeman Gilmore]

Aaron:
I just had a chance to go over this. Your details helped all makes
sense to me,  Thank you for your time, greatly appreciated.
ƒg

On Fri, May 8, 2020 at 1:44 AM Aaron Hill <address@hidden> wrote:
>
> On 2020-05-07 9:42 pm, Freeman Gilmore wrote:
> > On Thu, May 7, 2020 at 11:32 PM Aaron Hill <address@hidden>
> > wrote:
> >> %%%%
> >> \version "2.20.0"
> >>
> >> sum =
> >> #(define-void-function
> >>    (args)
> >>    (number-list?)
> > I know the the function uses a list for this because of the
> > undetermined number of args as the lambda procedure did.   In
> > (number-list?) how do you know what goes here, say it is not a number,
> > like a list of similes?
>
> You put whatever type predicate makes sense for the function.  The
> Notation Reference lists all of the predefined ones, whether they are
> primitives specified by R5RS (the Scheme standard that Guile follows) or
> defined by LilyPond itself.
>
> But you can also define your own type predicates:
>
> %%%%
> \version "2.20.0"
>
> #(define (flavor? x)
>    (member x '(vanilla chocolate strawberry)))
>
> cake =
> #(define-void-function
>    (flavor) (flavor?)
>    (format #t "\n~a cake is delicious!" flavor))
>
> \cake chocolate
>
> #(define (flavor-list? x)
>    (and (list? x)
>         (every flavor? x)))
>
> layeredCake =
> #(define-void-function
>    (flavors) (flavor-list?)
>    (format #t "\n~{~a~^ and ~} cake is delicious!" flavors))
>
> \layeredCake vanilla, strawberry
> %%%%
>
> ====
> GNU LilyPond 2.20.0
> Processing `type-predicate.ly'
> Parsing...
> chocolate cake is delicious!
> vanilla and strawberry cake is delicious!
> Success: compilation successfully completed
> ====
>
>
> >>    (format #t "\nargs: ~s, sum: ~s" args (apply + args)))
> > I do not have a clue what this all means "(format #t "\nargs: ~s, sum:
> > ~s" args"   Where can i find this information?
>
> See the documentation on Formatted Output [1].  I have shared a PDF
> version of the Guile 1.8 docs here [2] that makes a handy companion to
> the LilyPond docs for offline use.  Also included is the R5RS reference.
>
> [1]:
> https://www.gnu.org/software/guile/docs/docs-1.8/guile-ref/Formatted-Output.html#Formatted-Output
> [2]: https://drive.google.com/open?id=1WQ6zhMRUxf6-zdw3Gcv0SuuUI311Bu90
>
>
> >> \sum 2, 3, 5
> > Tried this and {a \sum2,3,5 b} (note spacing) and it worked, which is
> > what i was looking for.   But {a \sum 2, -3, 5 b} does not work?   How
> > to fix this so it does?
>
> Technically, when one says something like "2,3,5" in LilyPond, that is a
> key-list? as far as the parser's logic is concerned.  A "key" in this
> context refers to either an index (non-negative integer) or a symbol.
>
> To support general numbers, you will need to use Scheme syntax:
>
> %%%%
> \sum #'(1 -2/3 4.5)
> %%%%
> ====
> args: (1 -2/3 4.5), sum: 4.83333333333333
> ====
>
>
> -- Aaron Hill