Yes, I hadn't really thought through the semantics of define (i.e. whether 
it had let or letrec semantics). So, in my case, since I want let 
semantics, I will use let. I'm happy to follow the Racket style guide when 
I get to the point of contributing code that is covered by it, but I think 
I will use let, when I want let semantics, for my own code.

On Monday, March 11, 2019 at 1:17:47 PM UTC-4, Greg Hendershott wrote:
>
> To be fair: 
>
> As a new user, it's possible to have the intuition that `define` is 
> just a way to avoid indentation -- that it "writes a `let` for you, 
> from the point of the define to 'the end of the enclosing scope'". 
>
> And it's possible for that intuition to seem correct for a very long 
> time -- until you hit an example like Brian did. And then you need to 
> learn about `letrec`. 
>
> (As a non-new user, 99.9% of the time that I use a local `define` I 
> actually wish it were "like `let`" not `letrec`, but I use it anyway 
> and try to be careful.) 
>
>
> On Mon, Mar 11, 2019 at 12:29 PM Matthias Felleisen 
> <matt...@felleisen.org <javascript:>> wrote: 
> > 
> > 
> > 
> > > On Mar 11, 2019, at 11:21 AM, Brian Adkins <lojic...@gmail.com 
> <javascript:>> 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 
> > 
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