[racket] recursion style question

Well, I think you answer your own question with good reasons in the
last paragraph. :)

If `acc` is an implementation detail, let's not expose it as a parameter.[1]

At least, let's not do this for a function provided by a module.
Especially not a function with a contract and/or documentation.

But if it's a helper function that's not provided? Especially in a
small module? Then I'd say it doesn't matter so much.


[1]: Not even a parameter with a default value of '(), which is a 3rd
possibility -- a way to try to have your cake and eat it, too. You
could even have provide/contract insist that the value be '(), for
"outsiders"... but inside the module the contract is N/A. I actually
did this once upon a time. I changed my mind when I started to write
documentation for the function, got to that parameter, and realized...
yeah, nope. :)


On Sat, Sep 6, 2014 at 9:55 PM, Kevin Forchione <lysseus at gmail.com> wrote:
> Hi guys,
> Which is preferable?
>
> (define (foo let … (acc empty)) … (foo (rest let) ... (cons …. acc))
>
> or
>
> (define (foo lst ...) (let loop ([lst lst] …[acc empty]) … (loop (rest let) … (cons …. acc)))
>
> On the one hand we eliminate the named let construct, but on the other hand we expose the acc in the function / contract.  If the acc is not something the caller would ever need to know about, should we hide it inside the definition?
>
> -Kevin
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