On Tue, 22 Jun 2010 12:22:52 +0200 Mate Nagy <mn...@port70.net> wrote:
> On Tue, Jun 22, 2010 at 03:10:27AM -0700, Robert Ransom wrote:
> > Scheme *should* be used for everything because at least one good macro
> > system has been designed for it. Lisp macros can do arbitrary
> > computation at compile-time, and the Scheme macro system required by
> > R6RS provides all the power of Lisp macros *and* supports a
> > pattern-matching macro specification syntax for simple syntactic sugar.
> this is exactly the reason scheme macros are horrible and Lisp macros
> are better for your mind and health. This is one of the humongous,
> indefensible warts on the scheme language (the other being #f)
To get rid of #F in IF:
(define-syntax if
(syntax-rules ()
((if test true-exp false-exp)
(sys:if (eq? test '()) true-exp false-exp))
((if test true-exp)
(sys:if (eq? test '()) true-exp))))
To de-#F predicates:
(define-syntax sys-name
(lambda (exp)
(datum->syntax
exp
(string->symbol
(string-append
"sys:"
(symbol->string
(syntax->datum exp)))))))
(define-syntax de-false-semi-predicate
(syntax-rules ()
((de-false-semi-predicate pred-name)
(define (pred-name . args)
(sys:or (apply (sys-name pred-name) args) '())))))
(define-syntax de-false-predicate
(syntax-rules ()
((de-false-predicate pred-name)
(define (pred-name . args)
(sys:if (apply (sys-name pred-name) args)
't
'())))))
Zapping #F elsewhere is another SMOP, much easier than implementing the
sufficiently smart compiler. In any non-Lisp language, this would also
require hacking on the compiler.
Robert Ransom
signature.asc
Description: PGP signature
