changing a specific index bit in a binary number in Scheme(Racket) -

i need implement in scheme possibility change specific bit in binary number.

the input : 1.binary number , 2.index of bit change, 3.value set in index.

how can implemented?

here beginning of solution. can see what's need done in remaining case?

; bit-index->number : natural -> natural ;  return number in binary notation has 1 in position n ;  , has zeros elsewhere (define (bit-index->number n)   (expt 2 n))  ; example (displayln (number->string (bit-index->number 3) 2)) ; 1000  ; is-bit-set? : index natural -> boolean ;   bit n set in number x? (define (is-bit-set? n x)   ; bitwise-and 0 unless bit n set in number x   (not (zero? (bitwise-and (bit-index->number n) x))))  (define (set-bit! n x b)     (cond     [(= b 1) ; need set bit n in x 1      (cond        [(is-bit-set? n x) x]                             ; set        [else              (+ x (bit-index->number n))])] ; add 2^n     [(= b 0)      ; <what goes here?>      ]))