Re: where to put useful lists in the docs?

[Mark Polesky]

Mark Polesky wrote:
> I've updated ly:sort-alist to cope with non-numeric values.
> Here they are again:

oops. the last ly:sort-alist won't work. This one will.

(define (ly:sort-alist alist prop)
  #! Return a sorted list of pairs (entry . prop-value) of "alist"
  entries that have "prop" as a key. !#
  (let ((value (lambda (a) (ly:assoc-get prop (cdr a)))))
    (sort-list (map (lambda (a) (cons (car a) (value a)))
                    (filter value alist))
               (lambda (a b)
                 (if (number? (cdr a))     
                     (< (cdr a) (cdr b))
                     (string<? (symbol->string (cdr a))
                               (symbol->string (cdr b))))))))

(define (ly:filter-alist alist prop . value)
  #! Return a list of "alist" entries that have "prop" as a key (if
  "value" is unspecified), or that have "prop" set to "value" (if
  specified), or that do *not* have "prop" as a key (if "value" is
  'unset). !#
  (map car
       (filter
         (lambda (entry) 
           (let ((this-value (ly:assoc-get prop (cdr entry) 'unset)))
             (if (null? value)
                 (not (eq? this-value 'unset))   ; value is set.
                 (eq? (car value) this-value)))) ; value is a match.
         alist)))


test flexible sorting:
;(display (ly:sort-alist all-grob-descriptions 'outside-staff-priority))
;(display (ly:sort-alist all-grob-descriptions 'break-align-symbol))