SICP Exercise 1.32-1.33

(define (accumulate combiner null-value term a next b)
  (if (> a b)
      null-value
      (combiner (term a )
        (accumulate combiner null-value term (next a) next b)
        )
      )
  )

(define (accumulate-iter combiner null-value term a next b)
  (define (iter null-value a b)
    (if (> a b)
        null-value
        (iter (combiner null-value (term a)) (next a) b)
        )
    )
  (iter null-value a b)
  )

(define (inc n) (+ n 1))  
   
(define (cube a) (* a a a))

(define (sum term a next b)  
  (accumulate + 0 term a next b)
  )
(define (sum-iter term a next b)  
  (accumulate-iter + 0 term a next b)
  )

(define (sum-cubes a b)    
  (sum cube a inc b)
  )  
(define (sum-cubes-iter a b)    
  (sum-iter cube a inc b)
  )  

(sum-cubes 1 10) 
(sum-cubes-iter 1 10) 

 

(define (filtered-accumulate combainer filter? null-value term a next b)
  (if (> a b)
      null-value
      (if (filter? a)
          (combainer (term a) (filtered-accumulate combainer filter? null-value term (next a) next b))
          (filtered-accumulate combainer filter? null-value term (next a) next b)
          )
      )
  )

(define (isok a) (= a a))

(define (sum-filtered-accumulate term a next b)
  (filtered-accumulate + isok 0 term a next b)
  )

(define (sum-filtered-accumulate-cubes a b)
  (sum-filtered-accumulate cube a inc b)
  )
(sum-filtered-accumulate-cubes 1 10)