[racket-dev] Math library initial commit almost ready; comments on issues welcome

From: Eli Barzilay (eli at barzilay.org)
Date: Fri Oct 5 08:39:56 EDT 2012

Yesterday, Matthias Felleisen wrote:
> I know 
> What I mean is an _abstraction mechanism_ inside of TR. Possibly
> something that nobody else has.


And a quick reminder -- below is the ancient hack I once did for such
things, maybe something like this would be easier now.  Possibly much
easier: if a type is (foo ...) and `foo' is phase-1-bound to a macro
(anything that is not a bound type), then just expand it -- so that in
Neil's case the code could be:

  (define-syntax-rule (Xs->Xs T ...) (case-> (T -> T) ...))
  (: foo : (Xs->Xs Zero Flonum Real Float-Complex Complex))

(Either way, this means that it's easy to create huge types, and
therefore stressing TR's not-too-fast typechecker, but it sounds like
not having an abstraction doesn't stand in Neil's way to write huge
types anyway.)

  #lang typed-scheme
  (require (for-syntax scheme/base scheme/private/at-syntax))
  ;; (define-syntax (STX stx)
  ;;   (syntax-case stx ()
  ;;     [(_ expr) (at-syntax #'expr)]))
  (define-syntax (:: stx)
    (syntax-case stx (:)
      [(_ name : x ...)
       (with-syntax ([(x ...) (map at-syntax (syntax->list #'(x ...)))])
         #`(: name : x ...))]))
  (define-for-syntax Number #'Number)
  (define-for-syntax (T1 . -> . T2) #`(#,T1 -> #,T2))
  (:: twice : (let ([n (Number . -> . Number)])
                (n . -> . n)))
  (define (twice f) (lambda (x) (f (f x))))
  ((twice add1) 10)

          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!

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