info
Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
anaphoric lambda
33 views
Skip to first unread message
Robert L.
Mar 6, 2022, 4:40:20 AM3/6/22
to
A limited anaphoric lambda implemented with syntax-rules.
Examples:
(append-map (& list u u) '(a b c d))
===>
(a a b b c c d d)
((& / v (+ u u)) 2 88)
===>
22
(map (& string-append u (symbol->string v))
'("foo" "back")
'(bar track))
===>
("foobar" "backtrack")
(for-each
(& print (string-append u "-" v "-" w))
'("tick" "nick")
'("tock" "knock")
'("tack" "knack"))
===>
tick-tock-tack
nick-knock-knack
I'm not a macro guru, so this can probably be improved.
(define-syntax &-aux
(syntax-rules (u v w quote)
[(_ whole shadow (param ...) () original)
(lambda (param ...) original)]
[(_ (u more ...) (x y ...) () ps original)
(&-aux (more ...) (y ...) (x) ps original)]
[(_ (v more ...) (x y ...) (a) ps original)
(&-aux (more ...) (y ...) (a x) ps original)]
[(_ (w more ...) (x y ...) (a b) ps original)
(&-aux (more ...) (y ...) (a b x) ps original)]
[(_ ((quote ...) more ...) (y z ...) params ps original)
(&-aux (more ...) (z ...) params ps original)]
[(_ ('x more ...) (y z ...) params ps original)
(&-aux (more ...) (z ...) params ps original)]
[(_ ((s ...) more ...) (y z ...) params ps original)
(&-aux (s ... more ...) (s ... z ...) params ps original)]
[(_ (x more ...) (y z ...) params ps original)
(&-aux (more ...) (z ...) params ps original)]
[(_ () shadow params (p ps ...) original)
(&-aux original original params (ps ...) original)]))
;; Lambda with anaphoric parameters u, v, and w.
(define-syntax &
(syntax-rules ()
[(& x ...)
(&-aux (x ...) (x ...) () (1 2 3) (x ...))]))
Examples:
(append-map (& list u u) '(a b c d))
===>
(a a b b c c d d)
((& / v (+ u u)) 2 88)
===>
22
(map (& string-append u (symbol->string v))
'("foo" "back")
'(bar track))
===>
("foobar" "backtrack")
(for-each
(& print (string-append u "-" v "-" w))
'("tick" "nick")
'("tock" "knock")
'("tack" "knack"))
===>
tick-tock-tack
nick-knock-knack
I'm not a macro guru, so this can probably be improved.
(define-syntax &-aux
(syntax-rules (u v w quote)
[(_ whole shadow (param ...) () original)
(lambda (param ...) original)]
[(_ (u more ...) (x y ...) () ps original)
(&-aux (more ...) (y ...) (x) ps original)]
[(_ (v more ...) (x y ...) (a) ps original)
(&-aux (more ...) (y ...) (a x) ps original)]
[(_ (w more ...) (x y ...) (a b) ps original)
(&-aux (more ...) (y ...) (a b x) ps original)]
[(_ ((quote ...) more ...) (y z ...) params ps original)
(&-aux (more ...) (z ...) params ps original)]
[(_ ('x more ...) (y z ...) params ps original)
(&-aux (more ...) (z ...) params ps original)]
[(_ ((s ...) more ...) (y z ...) params ps original)
(&-aux (s ... more ...) (s ... z ...) params ps original)]
[(_ (x more ...) (y z ...) params ps original)
(&-aux (more ...) (z ...) params ps original)]
[(_ () shadow params (p ps ...) original)
(&-aux original original params (ps ...) original)]))
;; Lambda with anaphoric parameters u, v, and w.
(define-syntax &
(syntax-rules ()
[(& x ...)
(&-aux (x ...) (x ...) () (1 2 3) (x ...))]))
Robert L.
Mar 12, 2022, 10:38:12 PM3/12/22
to
On 3/6/2022, Robert L. wrote:
> A limited anaphoric lambda implemented with syntax-rules.
>
> Examples:
>
> (append-map (& list u u) '(a b c d))
> ===>
> (a a b b c c d d)
>
>
> ((& / v (+ u u)) 2 88)
> ===>
> 22
>
>
> (map (& string-append u (symbol->string v))
> '("foo" "back")
> '(bar track))
> ===>
> ("foobar" "backtrack")
>
>
> (for-each
> (& print (string-append u "-" v "-" w))
> '("tick" "nick")
> '("tock" "knock")
> '("tack" "knack"))
> ===>
> tick-tock-tack
> nick-knock-knack
Somewhat shorter and simpler:
> A limited anaphoric lambda implemented with syntax-rules.
>
> Examples:
>
> (append-map (& list u u) '(a b c d))
> ===>
> (a a b b c c d d)
>
>
> ((& / v (+ u u)) 2 88)
> ===>
> 22
>
>
> (map (& string-append u (symbol->string v))
> '("foo" "back")
> '(bar track))
> ===>
> ("foobar" "backtrack")
>
>
> (for-each
> (& print (string-append u "-" v "-" w))
> '("tick" "nick")
> '("tock" "knock")
> '("tack" "knack"))
> ===>
> tick-tock-tack
> nick-knock-knack
(define-syntax &-aux
(syntax-rules (u v w quote)
(lambda (param ...) original)]
[(_ (u more ...) (x y ...) () original)
(&-aux original original (x) original)]
[(_ (v more ...) (x y ...) (a) original)
(&-aux original original (a x) original)]
[(_ (w more ...) (x y ...) (a b) original)
(&-aux () () (a b x) original)]
[(_ ((quote ...) more ...) (y z ...) params original)
(&-aux (more ...) (z ...) params original)]
[(_ ('x more ...) (y z ...) params original)
(&-aux (more ...) (z ...) params original)]
[(_ ((s ...) more ...) (y z ...) params original)
(&-aux (s ... more ...) (s ... z ...) params original)]
[(_ (x more ...) (y z ...) params original)
(&-aux (more ...) (z ...) params original)]))
;; Lambda with anaphoric parameters u, v, and w.
(define-syntax &
(syntax-rules ()
[(& x ...)
Robert L.
Mar 24, 2022, 3:53:23 AM3/24/22
to
On 3/6/2022, Robert L. wrote:
[(_ () shadow (param ...) original)
(lambda (param ...) original)]
[(_ (u more ...) (x y ...) () original)
(&-aux original original (x) original)]
[(_ (v more ...) (x y ...) (a) original)
(&-aux original original (a x) original)]
[(_ (w more ...) (x y ...) (a b) original)
(&-aux () () (a b x) original)]
[(_ ((lambda x ...) more ...) (y z ...) params original)
(&-aux original original (x) original)]
[(_ (v more ...) (x y ...) (a) original)
(&-aux original original (a x) original)]
[(_ (w more ...) (x y ...) (a b) original)
(&-aux () () (a b x) original)]
(&-aux (more ...) (z ...) params original)]
[(_ ((& x ...) more ...) (y z ...) params original)
(&-aux (more ...) (z ...) params original)]
[(_ ((quote x ...) more ...) (y z ...) params original)
(&-aux (more ...) (z ...) params original)]
[(_ ('x more ...) (y z ...) params original)
(&-aux (more ...) (z ...) params original)]
[(_ ((s ...) more ...) (y z ...) params original)
(&-aux (s ... more ...) (s ... z ...) params original)]
[(_ (x more ...) (y z ...) params original)
(&-aux (more ...) (z ...) params original)]))
;; Lambda with anaphoric parameters u, v, and w.
(define-syntax &
(syntax-rules ()
[(& x ...)
(&-aux (x ...) (x ...) () (x ...))]))
(define-syntax &
(syntax-rules ()
[(& x ...)
0 new messages