Aaron Hill <lilyp...@hillvisions.com> writes: > On 2019-04-08 2:48 am, Thomas Morley wrote: >> foo = >> #(let ((x (cons 1 0))) >> (define-scheme-function (arg)(symbol?) >> (case arg >> ((indent) (set! x (cons (car x) (1+ (cdr x))))) >> ((increase) (set! x (cons (1+ (car x)) 0))) >> ((reset) (set! x (cons 1 0)))) >> (if (zero? (cdr x)) >> (format #f "~a" (car x)) >> (format #f "~a.~a" (car x) (cdr x))))) >> >> [ . . . ] >> >> I'm still not happy with those set-whatever!-thingies. I was beaten >> too often. Maybe someone comes up with a better approach. > > Using set! is perfectly fine as long as you encapsulate things well. > Your use of let to define a local variable minimizes the chance that > folks would be able to interfere with or even care about such > modification. However, your usage means there is still a "global" x > that is shared amongst all of the usage of foo.
There is no global variable x. There is a binding, but the scope of the binding ends with the let. This binding is anonymous afterwards and has no name. You can call functions manipulating the global variable x from inside of foo and their action is not related to having used the binding x when defining foo. -- David Kastrup _______________________________________________ lilypond-user mailing list lilypond-user@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-user
