[racket] Newbie question: Teach Yourself Scheme in Fixnum Days - macros

In case any lurkers like me are interested.
http://blog.racket-lang.org/2011/04/writing-syntax-case-macros.html

Stephen


On Tue, Apr 5, 2011 at 12:51 AM, Robby Findler
<robby at eecs.northwestern.edu>wrote:

> On Mon, Apr 4, 2011 at 6:25 PM, Eli Barzilay <eli at barzilay.org> wrote:
> > Four hours ago, Robby Findler wrote:
> >>
> >> It looks like a great macro essay for a certain crowd (altho the
> >> essay seems to insult that selfsame crowd; perhaps you are assuming
> >> that that crowd is into S&M?).
> >
> > Where's the insult?  (I didn't mean any insult -- the only thing I can
> > think of is the "nostalgia" reference, which is not an insult but the
> > often expressed sentiment for "a simple system, like `defmacro'".)
>
> Well, the scare quotes are a way to put down things, generally speaking.
>
> >
> >> Some comments:
> >>
> >>  - I probably would have used #` in the second while macro. Yes, I
> >> see you mention it later, but doing it at that point seems to fit
> >> with what the reader's been given at that point
> >
> > Well, that's one point where the purpose of the document is different
> > from a generic guide: my main goal was to write a quick intro to
> > people who are familiar with `defmacro' -- so I wanted to make it very
> > clear that it's the same kind of thing, only with wrapped sexprs
> > instead of raw ones.  In this case, I think that the long route is
> > better -- it shows that the extra tools (like #`) make things easier
> > only after you're aware of what goes on (and the fact that there's no
> > complicated magic involved, which is the frequent complain against
> > `syntax-case').
>
> Yes, and the second while macro is a fine place to say that, in my
> opinion. Indeed, it seems like the most natural point to go to next
> and then to continue later to say what is happening with the # on the
> front. This is just how your text is already building (in a good way
> imo).
>
> >
> >>  - it would be good if you did some kind of a computation at compile
> >> time, preferably to demonstrate an interesting computation one
> >> should want to do at compile time. Maybe a macro that embeds a
> >> formatted source location into its output?
> >
> > Good idea, I'll add something.
> >
> >
> >>  - cpp macros are, I believe, based on lexemes, not strings (so you
> >> cannot have an unclosed string in a macro or something).
> >
> > Yeah, I couldn't find a way to phrase it better than stick a random
> > "roughly" in.  Using "lexemes" is a good word to describe it, but it's
> > a little too opaque -- any ideas for something more light?
>
> "lexical tokens, like strings, parens, ..."?
>
> >
> >> At least nowadays they are.
> >
> > Yes -- I definitely have used `#define's with a double-quote opener.
>
> I think you can still pass an arg to gcc to get the old behavior back.
>
> Robby
>
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