> (cons-stream 2 (cons-stream 3 the-empty-stream))
(2 . #<promise>)
> (cons-stream 2 (cons-stream 3 the-empty-stream))
> s
(2 . #<promise>)
> (head s)
2
> (tail s)
(3 . #<promise>)
> (head (tail s))
3
> (tail (tail s))
()
[image] [image] b: undefined;
 cannot reference an identifier before its definition
> (head s)
2
> (tail s)
[image] [image] b: undefined;
 cannot reference an identifier before its definition
> (tail s)
[image] [image] b: undefined;
 cannot reference an identifier before its definition
> (define b 42)
> (tail s)
(42 . #<promise>)
> 
> (from-to 1 100)
(1 . #<promise>)
> (from-to 1 (fact 30000))
(1 . #<promise>)
> (define (from-to a b)
  (if (> a b) '()
      (cons a (from-to (+ a 1) b))))
> (length (from-to 1 (fact 30000)))
[image] Interactions disabled; out of memory
> (length (from-to 1 (fact 30000)))
[image] [image] mcdr: contract violation
  expected: mpair?
  given: #<promise>
> (length (from-to 1 (fact 30000)))
> (from-to 1 (fact 30000))
[image] Interactions disabled; out of memory

> (from-to 1 (fact 30000))
(1 . #<promise>)
> 
> (take 10 (enum 1 (fact 100)))
(1 2 3 4 5 6 7 8 9 10)
> (find-stream (lambda (x) (> x 10)) (enum 1 (fact 100)))
(11 . #<promise>)
> (find-stream (lambda (x) (> x 10)) (enum 1 (fact 100)))
(11 . #<promise>)
> (find-stream (lambda (x) (> x 10)) (from 1))
(11 . #<promise>)
> (find-stream (lambda (x) (< x 0)) (from 1))
[image] [image] user break
> nats
(0 . #<promise>)
> (find-stream (lambda (x) (> x 10)) nats)
(11 . #<promise>)
> (take 10 nats)
(0 1 2 3 4 5 6 7 8 9)
> (take 10 fibs)
(0 1 1 2 3 5 8 13 21 34)
> (take 100 fibs)
(0
 1
 1
 2
 3
 5
 8
 13
 21
 34
 55
 89
 144
 233
 377
 610
 987
 1597
 2584
 4181
 6765
 10946
 17711
 28657
 46368
 75025
 121393
 196418
 317811
 514229
 832040
 1346269
 2178309
 3524578
 5702887
 9227465
 14930352
 24157817
 39088169
 63245986
 102334155
 165580141
 267914296
 433494437
 701408733
 1134903170
 1836311903
 2971215073
 4807526976
 7778742049
 12586269025
 20365011074
 32951280099
 53316291173
 86267571272
 139583862445
 225851433717
 365435296162
 591286729879
 956722026041
 1548008755920
 2504730781961
 4052739537881
 6557470319842
 10610209857723
 17167680177565
 27777890035288
 44945570212853
 72723460248141
 117669030460994
 190392490709135
 308061521170129
 498454011879264
 806515533049393
 1304969544928657
 2111485077978050
 3416454622906707
 5527939700884757
 8944394323791464
 14472334024676221
 23416728348467685
 37889062373143906
 61305790721611591
 99194853094755497
 160500643816367088
 259695496911122585
 420196140727489673
 679891637638612258
 1100087778366101931
 1779979416004714189
 2880067194370816120
 4660046610375530309
 7540113804746346429
 12200160415121876738
 19740274219868223167
 31940434634990099905
 51680708854858323072
 83621143489848422977
 135301852344706746049
 218922995834555169026)
> 
> (map-stream 1+ nats)
(1 . #<promise>)
> (take 10 (map-stream 1+ nats))
(1 2 3 4 5 6 7 8 9 10)
> (take 10 (map-stream 1+ fibs))
(1 2 2 3 4 6 9 14 22 35)
> (take 10 (filter-stream odd? s))
[image] [image] b: undefined;
 cannot reference an identifier before its definition
> (take 10 (filter-stream odd? nats))
(1 3 5 7 9 11 13 15 17 19)
> (take 10 (filter-stream odd? fibs))
(1 1 3 5 13 21 55 89 233 377)
> (define (zip-streams
> (zip-streams + nats nats)
(0 . #<promise>)
> (take 10 (zip-streams + nats nats))
(0 2 4 6 8 10 12 14 16 18)
> ones
(1 . #<promise>)
> (take 10 ones)
(1 1 1 1 1 1 1 1 1 1)
> (take 10 (zip-streams + ones ones))
(2 2 2 2 2 2 2 2 2 2)
> (take 10 (zip-streams + ones nats))
(1 2 3 4 5 6 7 8 9 10)
> (take 10 (map-stream 1+ nats))
(1 2 3 4 5 6 7 8 9 10)
> (take 10 nats)
(0 1 2 3 4 5 6 7 8 9)
> 

> '(+ 5 a)
(+ 5 a)
> (delay (+ 5 a))
#<promise>
> (define code '(+ 5 a))
> (set-car! code '-)
> code
(- 5 a)
> (define code2 '(define (f a) code))
> code2
(define (f a) code)
> (define code2 (list 'define '(f a) code))
> code
(- 5 a)
> code2
(define (f a) (- 5 a))
> ones
(1 . #<promise>)
> (take 12493294832948 (enum 1 10))
(1 2 3 4 5 6 7 8 9 10)
> (enum 1 10)
(1 . #<promise>)
> (head (take 30 fibs))
[image] [image] map-stream: arity mismatch;
 the expected number of arguments does not match the given number
  expected: 2
  given: 3
> (head (take 30 fibs))
0
> (list-ref 29 (take 30 fibs))
[image] [image] zero?: contract violation
  expected: number?
  given: (0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765 10946 17711 28657 46368 75025 121393 196418 317811 514229)
> (list-ref (take 30 fibs) 29)
514229
> (list-ref (take 300 fibs) 299)
137347080577163115432025771710279131845700275212767467264610201
> ((nondivisors 2) 10)
[image] [image] nondivisors: undefined;
 cannot reference an identifier before its definition
> ((nondivisor 2) 10)
#f
> ((nondivisor 2) 11)
#t
> 
> (take 10 pseudoprimes)
(2 1 3 5 7 9 11 13 15 17)
> (take 10 pseudoprimes)
[image] [image] primes: undefined;
 cannot reference an identifier before its definition
> (take 10 pseudoprimes)
[image] Interactions disabled; out of memory
> (take 10 (sieve nats))
(2 1 3 5 7 9 11 13 15 17)
> (take 10 (from 2))
(2 3 4 5 6 7 8 9 10 11)
> (take 10 (sieve (from 2)))
(2 3 5 7 9 11 13 15 17 19)
> (take 10 (sieve (from 2)))
(2 3 5 7 9 11 13 15 17 19)
> (take 10 (sieve (from 2)))
(2 3 5 7 9 11 13 15 17 19)
> (take 10 (sieve (from 2)))
(2 3 5 7 11 13 17 19 23 29)
> (take 50 (sieve (from 2)))
(2
 3
 5
 7
 11
 13
 17
 19
 23
 29
 31
 37
 41
 43
 47
 53
 59
 61
 67
 71
 73
 79
 83
 89
 97
 101
 103
 107
 109
 113
 127
 131
 137
 139
 149
 151
 157
 163
 167
 173
 179
 181
 191
 193
 197
 199
 211
 223
 227
 229)
> (length (take 500 (sieve (from 2))))
500
> (length (take 500 (sieve (from 2))))
500
> (length (take 10000 (sieve (from 2))))
[image] [image] user break
> (length (take 1000 (sieve (from 2))))
1000
> (take 10 primes)
(2 3 5 7 11 13 17 19 23 29)