> On Mar 11, 2019, at 11:21 AM, Brian Adkins <[email protected]> wrote:
>
> I just discovered that define will fail at runtime, where let would fail at
> compile time. Besides helping to keep the indentation level from marching to
> the right "too much", what are the benefits of define over let?
>
> --- snip ---
> #lang racket
>
> (define (f n) (+ n 1))
>
> (define (foo)
> (define b (f a))
> (define a 7)
>
> b)
>
> (define (bar)
> (let ([b (f a)]
> [a 7])
>
> b))
> --- snip ---
I think your characterization is a bit misleading here.
In ‘bar’ ‘a’ is not bound, something that Racket (and DrRacket) properly signal
at compile time.
In ‘foo’ ‘a’ *is* bound, because you’ve set up a mutually recursive scope. But,
when Racket evaluates (foo) it notices that ‘a’ is bound but uninitialized,
which is two different things.
If you want to compare apples to apples, use a ‘letrec' instead of a ‘let' in
‘bar'. Then you have (1) the same semantics and (2) the same error.
— Matthias
--
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
