gistfile1.txt

Benchmark: ran giterate0, giterate0-1, giterate0-2, giterate1, giterate1-1, giterate2, each for 10 times.
    giterate0: 14.390 real, 21.430 cpu (21.250 user + 0.180 sys)@0.47/s n=10
  giterate0-1:  6.278 real,  6.270 cpu ( 6.270 user + 0.000 sys)@1.59/s n=10
  giterate0-2:  6.561 real,  6.560 cpu ( 6.560 user + 0.000 sys)@1.52/s n=10
    giterate1:  7.057 real,  7.050 cpu ( 7.050 user + 0.000 sys)@1.42/s n=10
  giterate1-1:  6.960 real,  6.960 cpu ( 6.960 user + 0.000 sys)@1.44/s n=10
    giterate2:  5.934 real,  5.930 cpu ( 5.930 user + 0.000 sys)@1.69/s n=10

              Rate giterate0 giterate0-1 giterate0-2 giterate1 giterate1-1 giterate2
    giterate0  0/s        --       0.293       0.306     0.329       0.325     0.277
  giterate0-1  2/s     3.418          --       1.046     1.124       1.110     0.946
  giterate0-2  2/s     3.267       0.956          --     1.075       1.061     0.904
    giterate1  1/s     3.040       0.889       0.930        --       0.987     0.841
  giterate1-1  1/s     3.079       0.901       0.943     1.013          --     0.852
    giterate2  2/s     3.614       1.057       1.106     1.189       1.174        --

t.scm

(use gauche.time)
(use gauche.generator)

(define (giterate0 f x)
  (^[]
    (begin0 x
      (set! x (f x)))))

(define (giterate0-1 f x)
  (^[]
    (rlet1 x_ x
      (set! x (f x)))))

(define (giterate0-2 f x)
  (let ((x_ x))
    (^[]
      (set! x_ x)
      (set! x (f x))
      x_)))

(define (giterate1 f x)
  (gcons* x
          (^[]
            (set! x (f x))
            x)))

(define (gcons1 item g)
  (define (gen)
    (set! gen g)
    item)
  (^[] (gen)))

(define (giterate1-1 f x)
  (gcons1 x
          (^[]
            (set! x (f x))
            x)))

(define (giterate2 f x)
  (^[]
    (set! x (f x))
    x))

(define (runner proc)
  (^[] ((gdrop (proc (cut + 1 <>) 1) 10000000))))

(define (main args)
  (time-these/report
   10
   `((giterate0   . ,(runner giterate0))
     (giterate0-1 . ,(runner giterate0-1)) 
     (giterate0-2 . ,(runner giterate0-2))
     (giterate1   . ,(runner giterate1))
     (giterate1-1 . ,(runner giterate1-1))
     (giterate2   . ,(runner giterate2))
     )))