On 6/25/09 4:51 PM, "Mark Polesky" <markpole...@yahoo.com> wrote:
>
>
> Here are 2 versions of the same procedure.
> Is the second one *too* concise and cryptic?
> - Mark
I actually like the general format of the second one better.
But I'd rewrite it a bit: It's a string-compare-<? function, so keep the
-<, and it's a predicate, so it should have a ?
(define (ly:string-compare-<? a b ci)
(let ((mismatch (first-diff-chars a b ci)))
(cond ((not mismatch) #f) ; a and b are equal
;; now I know mismatch is not #f, so I can use it safely
((not (car mismatch)) #t) ; a is an initial substring of b
((not (cdr mismatch)) #f) ; b is an initial substring of a
(else ; a and b have different characters
((if ci ly:char-ci<? ly:char<?)
(car mismatch) (cdr mismatch)))))))
Whenever I write a (cond ), I like to be able to express the outcome of each
alternative in language that is easily understood. In some cases, the code
itself does it. In this case, because first-diff-chars is a function with
a difficult return, I needed to remember the different outcomes of
first-diff-chars. Then I wanted a cond clause for each possible outcome,
so that's why I wrote it this way.
HTH,
Carl
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