[racket] Nested scope in D vs Racket

Hmm...I think I missed a distinction in modularity.  The quote says nested
scopes don't directly aid in providing separate library file modularity.
But the abstraction example I used was inner function modularity which does
not span multiple files.

The given rationale makes sense only in the context of multi-file
modularity?

-Paul

> -----Original Message-----
> From: users-bounces at racket-lang.org [mailto:users-bounces at racket-lang.org]
> On Behalf Of Paul Ojanen
> Sent: Saturday, August 21, 2010 8:17 AM
> To: 'Eduardo Cavazos'; users at racket-lang.org
> Subject: Re: [racket] Nested scope in D vs Racket
> 
> How about these two points from the referenced rationale:
> 
> 1. "Allowing global symbol masking is necessary for writing good modular
> code that's assembled out of separately compiled parts..."
> 
> 2. "...enclosing-scope masking is useless as a modularity device..."
> 
> 
> #1 What exactly is global symbol masking?
> I have been forced to learn the options of require due to naming
> conflicts.
> Is this global masking not being allowed?  Or are my require conflicts
> problematic because my imported identifiers are coming in AT THE SAME
> LEVEL?
> Perhaps global symbol masking says you are allowed to shadow only global
> variables, but not globally.  That is, global variables can be shadowed
> but
> only from within a nested scope.
> 
> #2 I get the impression that Racket/HtDP thinks opposite to the second
> quote.  local is given a lot of detailed attention in Intermezzo 3 of
> HtDP/1e, which ends by discussing nested scopes and demonstrating name
> reuse.  local is important for abstraction and, due to the importance of
> meaningful variable names, I would say enclosing-scope masking is very
> important as a feature.  Not necessary but certainly not useless.
> 
> -Paul
> 
> > -----Original Message-----
> > From: users-bounces at racket-lang.org [mailto:users-bounces at racket-
> lang.org]
> > On Behalf Of Eduardo Cavazos
> > Sent: Saturday, August 21, 2010 3:33 AM
> > To: users at racket-lang.org
> > Subject: [racket] Nested scope in D vs Racket
> >
> > Hello,
> >
> > The first example in this note is illegal in the D programming language:
> >
> > http://lists.puremagic.com/pipermail/digitalmars-d/2010-
> August/081424.html
> >
> > Coming from a Scheme background, I was surprised as this is allowed in
> > Scheme. I.e. this is the quivalent code in Scheme:
> >
> > (let ((a 20))
> >    (let ((a 30))
> >      ...))
> >
> > Andrei Alexandrescu pointed out the rationale for this design decision
> > here:
> >
> > http://lists.puremagic.com/pipermail/digitalmars-d/2010-
> August/081430.html
> >
> > It sounds like the D designers are "protecting" the programmers. The
> > Racket team is of course concerned with the "teachability" of their
> > languages and have experience with the known pitfalls in languages. So
> > my question is, do any Racket people agree with the rationale provided
> > by the D guys? In all your years of teaching Scheme/Racket, has this
> > situation of shadowing names been a problem? (I've always seen it as a
> > feature, even C supports it.)
> >
> > Ed
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