[racket] Use `set!' or not in this scenario?

The process of lambda dropping can also solve your problem.

In essence, make f2 to fx local function definitions inside f1. This
eliminates the need for  the-data to be an explicit parameter given that f2
through fx would be within the lexical scope of the-data. This assumes, of
course, that f2 through fx are not called by other functions in your
program.

Marco



On Fri, Jul 19, 2013 at 12:23 PM, Ben Duan <yfefyf at gmail.com> wrote:

> Scenario: A piece of data is determined in the first function `f1', but is
> only processed in a sub-sub-sub-… function `fx'.
>
> One way is to use pass `the-data' as arguments from `f1' through `f2' all
> the way down to `fx':
>
>     (define f1 (the-data …)
>       …
>       (f2 the-data …)
>       …)
>
>     (define f2 (the-data …)
>       …
>       (f3 the-data …)
>       …)
>
>     …
>
>     (define fx (the-data …)
>       … the-data …)
>
> But in the above way, the body of `f2', `f3', `f4' and so on doesn't use
> `the-data'. It is only passed to the next function. And I still have to add
> the argument `the-data'.
>
> Another way is to use `set!':
>
>     (define the-data …)
>
>     (define f1 (the-data …)
>       …
>       (set! the-data …)
>       …
>       (f2 …)
>       …)
>
>     (define f2 (…)
>       …
>       (f3 …)
>       …)
>
>     …
>
>     (define fx (…)
>       … the-data …)
>
> But in this way, the benefits of being functional are lost. For example
> there will be some problems writing tests for these functions.
>
> My question is, which way is better? Or are there other ways to solve this
> problem?
>
> Thanks,
> Ben
>
> P.S. This question is not about Racket. It's just a beginner's question
> about how to program. Please let me know if it's not appropriate to ask
> this kind of questions here. Thank you.
>
> ____________________
>   Racket Users list:
>   http://lists.racket-lang.org/users
>
>


-- 

Cheers,

Marco

Have a´¨)
¸.·´¸.·*´¨) ¸.·*¨)
(¸.·´ (¸.·´ * wonderful day! :)
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