[plt-scheme] to define, or to let

On Mar 19, 2004, at 7:17 AM, Joe Marshall wrote:

> Richard Cleis <rcleis at mac.com> writes:
>
>> 1) Do these two generate the same code?
>
> They might.  Or not.  They do the same thing.
>
>> 2) Which one best contains the spirit of scheme?
>>
>> (define a-function-using-defines
>>    (lambda ()
>>      (define one-variable 3)
>>      (define another-variable 4)
>>      (list one-variable another-variable))) ; edi
>>
>> (define a-function-using-let-list
>>    (lambda ()
>>      (let ((one-variable 3)
>>            (another-variable 4) )
>>        (list one-variable another-variable)))) ; edit
>
> I have a strong preference for the latter for a couple of reasons.
>
> The LET expression cannot have mutually recursive bindings, so I know
> without further inspection that no variable being bound in the LET
> depends on any of the others.
>
> The internal DEFINE is equivalent to a LETREC, and LETREC exists
> to facilitate defining mutually recursive functions and data
> structures.  When I see one, I tend to expect that earlier definitions
> may depend on later ones.
>
> But that's just my opinion.
>
Thanks.  I am diving into the scheme pool before anyone else in my 
group, now some are beginning to ask questions like these.  I have been 
using 'define only when absolutely necessary, but have no rigorous 
explanation.

rac