Scheme procedure problem

Posted by Zun on Stack Overflow See other posts from Stack Overflow or by Zun
Published on 2010-03-31T08:28:43Z Indexed on 2010/03/31 8:33 UTC
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Scheme

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sicp

I defined the Scheme procedure to return another procedure with 2 parameters :

(define (smooth f)
  (?(x dx)(/ (+ (f (- x dx))
             (f x)
             (f (+ x dx)))
          3.0)))

if i run this procedure with sin procedure with 2 arguments 10 and 0.0001 then it is ok

  ((smooth sin) 10 0.0001) ==> -0.544021109075966

if i run this procedure recursively, then it has error

((smooth (smooth sin)) 10 0.0001)
==> procedure expects 2 arguments, given 1: #<promise:temp6>

So can anyone tell me where is my problem? Thank you in advance !!!

PS:this is apart of exercise 1.44 in SICP

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