Question

On Dr Racket: write a scheme function that consumes a 9 digit function and an integer between 1 and 9 (inclusive). And produces a digit at the specified location. EX: (sin-digit 463290115 6) => 0: do not convert the 9 digit number to a string.

Answer 1

(define (int->list n)
(if (< n 10)
(list n)
(append (int->list (floor (/ n 10)))
(list (remainder n 10)))))

(define (foo l index)
(if (= index 1)
(car l)
(foo (cdr l) (sub1 index))))

(define (sin-digit n index)
(foo (int->list n) index))