; This function will not change the value of x value. 
; increment and decrement operators will change value of variable

;Valdegg@ Solution
(define (increment x)
  (+ 1 x) 
)
; defining a variable var with initial value 3
(define var 3)
(display (increment var)) (newline)
(display var) (newline)

;uselpa@ answer
(define-syntax incf
  (syntax-rules ()
    ((_ x)   (begin (set! x (+ x 1)) x))
    ((_ x n) (begin (set! x (+ x n)) x))))

(define-syntax decf
  (syntax-rules ()
    ((_ x)   (incf x -1))
    ((_ x n) (incf x (- n)))))
    
(display (incf var)) (newline)
(display var) (newline)