Urs Liska <li...@openlilylib.org> writes:
> Am 24.05.2018 um 09:56 schrieb Gianmaria Lari:
>> The following function increase a counter by 1 and return it as string
>>
>> #(define count 0)
>> #(define (nextcount) (begin
>> (set! count (+ 1 count))
>> (number->string count)
>> )
>> )
>>
>> Is my code ok, or I should write it in a different way?
>
> Two observations:
> - You don't need that (begin ...) wrapper because the procedure
> definition already behaves as such
> - You shouldn't use reserved words for variable names, so I'd use
> 'counter' instead.
>> Is it possible to define "count" inside the function just in case it
>> is undefined?
>
> Yes, see:
>
> \version "2.19.80"
>
> #(define (nextcount)
> (if (not (defined? 'counter)) (ly:parser-define! 'counter 0))
> (set! counter (+ 1 counter))
> (number->string counter)
> )
You actually don't need to define it externally:
#(define nextcount
(let ((counter 0))
(lambda ()
(set! counter (1+ counter))
(number->string counter))))
$(nextcount)
$(nextcount)
will work just fine.
--
David Kastrup
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