2015/12/09
SICP 問題 3.55
s0, s0 + s1, s0 + s1 + s2, ...
という要素なのでstreamの次の要素とsum-integersの今の要素を足したものがsum-integersの次の要素となる.
(define (partial-sums stream)
(cons-stream (stream-car stream)
(add-streams (stream-cdr stream)
sum-integers)))
(define sum-integers
(partial-sums integers))
gosh> (stream-ref sum-integers 0)
1
gosh> (stream-ref sum-integers 1)
3
gosh> (stream-ref sum-integers 2)
6
gosh> (stream-ref sum-integers 3)
10
gosh> (stream-ref sum-integers 4)
15