In case I want to grok this in 6 months.
(define (whatdoicallthis lst func) ;; Grab pointer to first cons. ;; Contents of car will be dropped. ;; Contents of cdr will be clobbered. (let ((newlst (list #t))) ;; acc is usually the result of the ;; "reduce so far", here it is the ;; last pair in newlis. cur is ;; current item of consideration ;; in the original list. (lfold (lambda (acc cur) ;; func should return a new ;; pair, which gets tacked ;; onto the end of newlst. (set-cdr! acc (func cur)) ;; Have lfold push the new ;; pair into acc next ;; time it loops. (rest acc)) newlst ; Accumulator lst) ; list we're deriving from (rest newlst))) ; car is trash, see above. (define (append hd tl) (whatdoicallthis hd (lambda (nxt) (cons nxt tl)))) (define (map func lst) (whatdoicallthis lst (lambda (nxt) (list (func nxt)))))
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