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Re: Opaque syntax objects



 Felix Winkelmann wrote:
 
 > On 8/12/05, Michael Sperber <sperber@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
 > > 
 > > The issue has come up in the discussion, but hasn't really been in the
 > > focus yet:
 > > 
 > > I'd like to suggest that compound expressions be represented by an
 > > opaque type rather than by pairs.  This would ensure a modicum of
 > > abstraction, and would *really* make comprehensive the ability of all
 > > syntax objects to carry location information.  I've come to appreciate
 > > this added layer of abstraction in PLT Scheme.
 > > 
 > 
 > But wouldn't this completely break the (IMHO) rather practical ability
 > to destructure arguments passed to macros via normal Scheme operators?
 > What I like about srfi-72 is that I can write hygienic macros with (nearly)
 > the same ease as in conventional Lisp-/quasiquote-style. 
 
 
 As a supporting data point, I was able to port the Scheme48 basic forms 
 (cond, case, etc. ...), as well as its syntax-rules implementation, a very
 nontrivial macro, with the greatest of ease to SRFI-72, without having to
 worry about converting cadddr's, null?'s, higher order list operations 
 such as map, every, ..., and so on.  I also did not have to worry that 
 some coercion might have changed the complexity class of the algorithm.