With Carl's help, I've created a new file that contains procedures
for sorting lists and alists according to a specific algorithm
that generates more intuitively-ordered lists, which will make it
a lot easier to locate things in the docs, for example.
I've attached the file here, but I haven't made a patch, because I
need to know a) if anyone wants to suggest any alterations before
Carl applies it, and b) precisely where should I enter
"lily-sort.scm" in the file "lily.scm" (there are procedures
defined publicly).
I'm interested in feedback regarding my selection and order of
ranked non-alphanumeric characters ( !?<=>:-_).
Also I think the initial comments are kind of lengthy, maybe
someone can comment on that, too.
Thanks.
- Mark
;; lily-sort.scm
;;
;; LilyPond-specific sorting of symbols, strings, and alists.
;;
;; (c) 2009 Mark Polesky
;;
;; This file implements a LilyPond-specific character-sorting algorithm
;; that can be used to sort lists, alists, etc. consistently and
;; predictably throughout the source code. The primary advantage of this
;; algorithm is that lists are sorted in a more intuitive way, which may
;; allow users to find items faster in the documentation.
;;
;; As an example, a user, looking in the documentation to see if there's
;; a function called "ly:grob?", might assume that there isn't one,
;; since it doesn't appear before "ly:grob-alist-chain" (using the
;; default sort).
;;
;; This happens because "-" comes before "?" in the default sort order.
;; But since "?" is more likely to come at the end of a scheme symbol, a
;; more intuitive sort can be achieved by reversing that order.
;;
;; Similarly, non-alphanumeric characters can be ranked in terms of how
;; likely one will be found closer to the end of a symbol. For example,
;; ":" is stronger separator than "-", as can be seen here:
;;
;; "ly:staff-symbol::print"
;; "ly:staff-symbol-referencer::callback"
;;
;; Intuitively, "staff-symbol-referencer" ought to come after
;; "staff-symbol", but since "-" comes before ":" in the default sort
;; order, these symbols are by default listed in the opposite order.
;;
;; Thus the algorithm implemented here ranks the following nine
;; characters (starting with the space character) in order from
;; most-to-least likely to terminate a symbol: " !?<=>:-_". That order
;; is defined in the "init-list" binding of the function
;; "ly:char-compare".
;;
;; Publicly defined binary predicates include:
;; ly:string<? ly:symbol<? ly:alist<?
;; and their case-insensitive counterparts:
;; ly:string-ci<? ly:symbol-ci<? ly:alist-ci<?
;;
;; Case-insensitive predicates are recommended in general; otherwise
;; symbols like "Y-offset" appear near the top of lists which
;; otherwise include mostly lowercase symbols.
(define (ly:char-compare a b ci)
(let* ((init-list (string->list " !?<=>:-_"))
(mem-a (member a init-list))
(mem-b (member b init-list)))
(cond ((and mem-a mem-b) (< (length mem-b) (length mem-a)))
(mem-a #t)
(mem-b #f)
(else ((if ci char-ci<? char<?) a b)))))
(define (ly:char<? a b)
(ly:char-compare a b #f))
(define (ly:char-ci<? a b)
(ly:char-compare a b #t))
(define (first-diff-chars str0 str1 ci)
(let loop ((a (string->list str0)) (b (string->list str1)))
(cond ((and (null? a) (null? b)) #f)
((null? a) (cons #f (car b)))
((null? b) (cons (car a) #f))
((not ((if ci char-ci=? char=?) (car a) (car b)))
(cons (car a) (car b)))
(else (loop (cdr a) (cdr b))))))
(define (ly:string-compare a b ci)
(let ((mismatch (first-diff-chars a b ci)))
(cond ((and mismatch (car mismatch) (cdr mismatch))
((if ci ly:char-ci<? ly:char<?)
(car mismatch) (cdr mismatch)))
((and mismatch (cdr mismatch)) #t)
(else #f))))
(define-public (ly:string<? a b)
"Return #t if string A is less than string B in case-sensitive
LilyPond sort order."
(ly:string-compare a b #f))
(define-public (ly:string-ci<? a b)
"Return #t if string A is less than string B in case-insensitive
LilyPond sort order."
(ly:string-compare a b #t))
(define-public (ly:symbol<? a b)
"Return #t if symbol A is less than symbol B in case-sensitive
LilyPond sort order."
(ly:string<? (symbol->string a) (symbol->string b)))
(define-public (ly:symbol-ci<? a b)
"Return #t if symbol A is less than symbol B in case-insensitive
LilyPond sort order."
(ly:string-ci<? (symbol->string a) (symbol->string b)))
(define-public (ly:alist<? a b)
"Return #t if the first key of alist A is less than the first key of
alist B, using case-sensitive LilyPond sort order. Keys are assumed to
be symbols."
(ly:string<? (symbol->string (car a))
(symbol->string (car b))))
(define-public (ly:alist-ci<? a b)
"Return #t if the first key of alist A is less than the first key of
alist B, using case-insensitive LilyPond sort order. Keys are assumed
to be symbols."
(ly:string-ci<? (symbol->string (car a))
(symbol->string (car b))))
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