Re: cheap-list

[Aaron Hill]

On 2020-05-07 6:54 pm, Freeman Gilmore wrote:
> That helps but I do not know how to use it.    For now that is OK    I
> found the places in “Notation Reference” where cheap-list was
> mentioned, that is why I asked.

It would be used in place of list? as a type predicate.  Consider:

%%%%
\version "2.20.0"

items =
#(define-void-function
  (items) (list?)
  (format #t "\nitems: ~s" items))

cheap-items =
#(define-void-function
  (items) (cheap-list?)
  (format #t "\ncheap-items: ~s" items))

\cheap-items #'(2 3 5)
\items #'(2 3 5)

\cheap-items #'(not a proper . list)
\items #'(not a proper . list)
%%%%

====
GNU LilyPond 2.20.0
Processing `cheap-list.ly'
Parsing...
cheap-items: (2 3 5)
items: (2 3 5)
cheap-items: (not a proper . list)
cheap-list.ly:17:8: error: wrong type for argument 1.  Expecting list,
  found (cons (quote not) (cons (quote a) (cons (quote proper) (quote 
list))))
\items
       #'(not a proper . list)
fatal error: failed files: "cheap-list.ly"
====


-- Aaron Hill