Boy I didn't even read the first line of your email.. anyway.. what
does "supercut" mean?
On 08/14/2010 03:02 PM, Jon Rafkind wrote:
Your library looks cool.. definately has more features than what I
made. What does 'scut' mean though? s-cut ?
On 08/14/2010 09:20 AM, Jay McCarthy wrote:
This is very similar to supercut:
http://github.com/jeapostrophe/exp/blob/master/scut.ss
scut allows you to put any expression inside it and it will turn it
into a function. The arguments come from use of _. If you have _i then
it will be the ith argument. If you have _string then the function
will take a "string" keyword argument. The function takes as many
arguments as the maximum i you use inside it. Finally, _... gives you
the rest arg. The bottom of that file has many examples, here are a
few:
((scut _0) 1) => 1
((scut (+ _0 (/ _1 _2)))
1 2 3)
=> (+ 1 (/ 2 3))
((scut (+ _lhs _lhs _rhs)) #:lhs 1 #:rhs 2)
=> 4
((scut (apply + _0 _...))
1 2 3)
=> 6
On Fri, Aug 13, 2010 at 11:01 PM, Jon Rafkind<[email protected]>
wrote:
I came up with this little hack that lets you avoid giving an
explicit
argument list to functions. Arguments are discovered by usages of
underscores followed by a number, like _1 and _2. Partly inspired by
scala;
sure to make your blood boil if you love hygiene.
;;; usage
(define/implicit foo1 (printf "~a ~a ~a\n" _8 _9 _8))
(foo1 5 12)
;;; code
#lang racket/base
(require (for-syntax racket/base
racket/list
syntax/parse
)
racket/stxparam)
(define-syntax-rule (implicits all thing ...)
(begin
(define-syntax-parameter thing (lambda (stx)
(raise-syntax-error #f (format "~a
can only
be used in a
define/implicit function" 'thing))))
...
(provide thing ...)
(define-for-syntax all (list #'thing ...))))
(implicits all-implicits _1 _2 _3 _4 _5 _6 _7 _8 _9 _10)
(provide define/implicit lambda/implicit)
(define-syntax (lambda/implicit stx)
(define (find-implicits stx)
(define-syntax-class implicit
[pattern x:identifier
#:when (ormap (lambda (y)
(free-identifier=?
y #'x))
all-implicits)])
(remove-duplicates
(filter values
(syntax-parse stx
[x:implicit (list #'x)]
[(x ...) (apply append (map find-implicits
(syntax->list #'(x
...))))]
[else (list #f)]))
free-identifier=?))
(syntax-parse stx
[(_ body ...)
(define implicit-arguments (find-implicits stx))
(with-syntax ([(new-arg ...) (generate-temporaries
implicit-arguments)]
[(implicit ...) implicit-arguments])
#'(lambda (new-arg ...)
(syntax-parameterize ([implicit (make-rename-transformer
#'new-arg)] ...)
body ...)))]))
(define-syntax-rule (define/implicit name body ...)
(define name (lambda/implicit body ...)))
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