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  • anaphoric lambda

    From Robert L.@21:1/5 to Thomas F. Burdick on Sun Mar 13 02:39:29 2022
    Thomas F. Burdick wrote:

    Pascal Costanza <pc@p-cos.net> writes:

    (loop for x in '(1 2 3)
    for y in '(4 5 6)
    collect (* 2 (+ x y)))

    vs.

    (mapcar (lambda (x y)
    (* 2 (+ x y)))
    '(1 2 3)
    '(4 5 6))

    Oh, that one's easy:

    (mapcar (compose (curry #'* 2) #'+)
    '(1 2 3) '(4 5 6))

    (map (& * 2 (+ u v)) '(1 2 3) '(4 5 6))
    ===>
    (10 14 18)

    Given:

    (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 ...))]))

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Robert L.@21:1/5 to Robert L. on Sun Mar 13 03:50:32 2022
    On 3/12/2022, Robert L. wrote:

    (map (& * 2 (+ u v)) '(1 2 3) '(4 5 6))
    ===>
    (10 14 18)

    Given:

    (define-syntax &-aux

    Better:

    (define-syntax &-aux
    (syntax-rules (u v w quote)
    [(_ () 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)]
    [(_ ((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 ...)
    (&-aux (x ...) (x ...) () (x ...))]))

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)