sicp-ex-1.44



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 (define dx 0.00001) 
  
 (define (smooth f) 
   (lambda (x) 
     (/ (+ (f (- x dx)) 
           (f x) 
           (f (+ x dx))) 
        3))) 
  
 (define (n-fold-smooth f n) 
   ((repeated smooth n) f)) 

The input needs only the function and the number of smoothing procedure, so it should not include x.