[racket] recursion style question

From: Marc Burns (m4burns at uwaterloo.ca)
Date: Sun Sep 7 00:41:51 EDT 2014

As Greg explained, the named let form simplifies the interface to other code. It is much more common in practice.

> On Sep 6, 2014, at 23:50, Greg Hendershott <greghendershott at gmail.com> wrote:
> 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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