src/sicp/ex3_77.rkt

   1 #lang racket
   2
   3 (define (integral integrand delayed-initial-value dt)
   4   (cons-stream initial-value
   5                (let ((integrand (force delayed-initial-value)))
   6                  (if (stream-null? integrand)
   7                      the-empty-stream
   8                      (integral (stream-cdr integrand)
   9                                (+ (* dt (stream-car integrand))
  10                                   initial-value)
  11                                dt)))))