練習問題4.18 (define (solve f y0 dt) (define y (integral (delay dy) y0 dt)) (define dy (stream-map f y)) y) (define (solve_ f y0 dt) (let ((y '*hoge*) (dy '*hoge*)) (let ((a (integral (delay dy) y0 dt)) (b (stream-map f y))) (set! y a) (se…