[plt-scheme] help.... Me :)

  plt-scheme at list.cs.brown.edu
   
   
  Please Help 
  I used to create a program in ( PLT SCHEMES ) it is a  set of intervals integers between two indicated numbers and my contain two numbers themselves : 
    Sample 
    r1 :  0 to 20 
    r2 : 2001 to 2008 
 
   " my problem is to set  operation intervals  "  
   
    ( interval – length r2 )  
  7 
    (Interval-print- all r2 )
     2002 2003 2004 2005 2006 2007 2008
     (interval-combine r1 r2 ) or ( interval-combine r2 r1 ) 
     makes an interval 0 to 2008 
       (interval-sum r1) 
returns the sum of all elements 
       (interval-mid r1) 
  the middle number in interval. If length is even, return the lower mid
   
  ( interval- print r1 ) 
  0,20 
     (interval-print-n r1 n) 
  prints first n elements of r1 ( less if length is lesser than n ) 
   
   
  “ thanks for your brilliant ideas please help me : ))  “  
   
   
  
       
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