[plt-scheme] "Hiding" a global variable

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solutions. Better to contact your instructor (you are paying them,
right?) or at least don't include solutions so your classmates don't
see them.

Robby

On Tue, Oct 20, 2009 at 10:00 PM, Mike <winhqwebmstr at gmail.com> wrote:
> Hello,
>
> I have a rather difficult homework question. I would like to know what
> direction to look in in order to solve it:
>
> "Develop a function named next that takes no arguments, but each time
> you call it, it returns how many times it has been called:
>
>> (next)
> 1
>> (next)
> 2
>> (next)
> 3
>
>
> Hint: You can do this with a global variable, but it would be "neater"
> if you could hide the variable. Think about local.... "
>
>
> I wrote the function implementing a global variable, as follows;
>
> (define times 0)
>
> ; next - returns how many times it has been called each time it is
> called
> ; @ none
> ; -> number
>
> (define (next)
>   (begin (set! times (add1 times))
>          times))
>
> I now need to make an implementation without using a global variable.
> Any suggestions?
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