gistfile1.scm

(define (map_ proc lis)
  (map1 proc lis 0))

(define (map1 proc lis n)
  (cond [(null? lis) '()]
        [(> n 30) (reverse (fold (^[elt r] (cons (proc elt) r)) '() lis))]
        [else (cons (proc (car lis)) (map1 proc (cdr lis) (+ n 1)))]))

#|
gosh> (use gauche.time)
#<undef>
gosh> (define data (iota 30))
data
gosh> (time-these/report '(cpu 5) `((tail+reverse . ,(cut map - data))
                                    (non-tail-rec . ,(cut map_ - data))))
Benchmark: ran tail+reverse, non-tail-rec, each for at least 5 cpu seconds.
  tail+reverse: 5.049 real, 5.060 cpu (5.060 user + 0.000 sys)@359966.60/s n=1821431
  non-tail-rec: 5.044 real, 5.080 cpu (5.080 user + 0.000 sys)@369097.44/s n=1875015

                   Rate tail+reverse non-tail-rec
  tail+reverse 359967/s           --        0.975
  non-tail-rec 369097/s        1.025           --
#<undef>
|#