Chapter 3, Modularity, Objects, and State

Exercise 3.77


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(define (integral delayed-integrand initial-value dt)
  (cons-stream initial-value
			   (let ((integrand (force delayed-integrand)))
				 (if (stream-null? integrand)
					 the-empty-stream
                     (integral (delay (stream-cdr integrand))
                               (+ (* dt (stream-car integrand))
                                  initial-value)
                               dt)))))