CODEWITHSUNDEEP
functional-programmingschemeracket
IntoTheDeep
IntoTheDeep

Reputation: 4118

Racket Scheme nested define

My target is to write method which by given х and n calculate the sum:

S = 1 + x/1! + x2/2! + ... + xn/n!

My code:

#lang racket
(define (func n)
  (define (n1! f)
    (if (= f 0) 1
        (* f (n1! (- f 1)))))
  (define (iter i res)
    (if (= i n) (+ 1 res)
       (iter (+ i 1) (/ i (n1! i))))))
(func 3)

There is error which I do not understand. It says:

begin (possibly implicit): no expression after a sequence of internal definitions in:
  (begin (define (n1! f) (if (= f 0) 1 (* f (n1! (- f 1))))) (define (iter i res) (if (= i n) (+ 1 res) (iter (+ i 1) (/ i (n1! i))))))
  (define (n1! f) (if (= f 0) 1 (* f (n1! (- f 1)))))
  (define (iter i res) (if (= i n) (+ 1 res) (iter (+ i 1) (/ i (n1! i)))))

What I do wrong?

Upvotes: 2

Views: 1041

Answers (1)

river
river

Reputation: 1028

You need to add an expression after the two defines, so that func will actually do something. Currently your code is equivalent to (define (func n)).

Your code is this

(define (func n)
  (define (n1! f)
    (if (= f 0) 1
        (* f (n1! (- f 1)))))
  (define (iter i res)
    (if (= i n) (+ 1 res)
       (iter (+ i 1) (/ i (n1! i))))))

you need to do this

(define (func n)
  (define (n1! f)
    (if (= f 0) 1
        (* f (n1! (- f 1)))))
  (define (iter i res)
    (if (= i n) (+ 1 res)
       (iter (+ i 1) (/ i (n1! i)))))
  (iter n 0))

Upvotes: 4

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