[Chicken-janitors] #11: replace ##sys#strip-syntax with version that handles cyclic structures

[Chicken Trac]

#11: replace ##sys#strip-syntax with version that handles cyclic structures
------------------------+---------------------------------------------------
Reporter:  felix        |       Owner:  felix         
    Type:  enhancement  |      Status:  new           
Priority:  minor        |   Component:  core libraries
 Version:  4.0.0        |    Keywords:                
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 Alex Shinn contributed this enhanced version (verify and replace):

 {{{
 (define (##sys#strip-syntax exp #!optional se alias)
  ;; if se is given, retain bound vars
  (let ((seen '()))
    (let walk ((x exp))
      (cond ((assq x seen) => cdr)
            ((symbol? x)
             (let ((x2 (if se
                           (lookup x se)
                           (get x '##core#macro-alias) ) ) )
               (cond ((get x '##core#real-name))
                     ((and alias (not (assq x se)))
                      (##sys#alias-global-hook x #f))
                     ((not x2) x)
                     ((pair? x2) x)
                     (else x2))))
            ((pair? x)
             (let ((cell (cons #f #f)))
               (set! seen (cons (cons x cell) seen))
               (set-car! cell (walk (car x)))
               (set-cdr! cell (walk (cdr x)))
               cell))
            ((vector? x)
             (let ((vec (make-vector (vector-length x))))
               (set! seen (cons (cons x vec) seen))
               (do ((ls (map walk (vector->list x)) (cdr ls)) (i 0 (+ i
 1)))
                   ((null? ls) vec)
                 (vector-set! vec i (car ls)))))
            (else x)))))
 }}}

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Ticket URL: <http://www.irp.oist.jp/trac/chicken/ticket/11>
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