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  1.  
  2. avg_([], Sum, Len, Avg) :- 
  3. 	Avg is Sum / Len.
  4. avg_(Arr, Sum, Len, Avg) :-
  5. 	append([Car], Cdr, Arr),
  6. 	Sum2 is Sum + Car,
  7. 	Len2 is Len + 1,
  8. 	avg_(Cdr, Sum2, Len2, Avg).
  9. avg(Arr, Avg) :-
  10. 	avg_(Arr, 0, 0, Avg).
  11.  
  12. main :- 
  13.     Lst1 = [1,2,3,4,5,6,7,8,9],
  14.     avg(Lst1, Avg),
  15.     print(Avg),
  16.     halt.
  17.  
  18. :- main.
Success #stdin #stdout 0.02s 6740KB
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https://ideone.com/3JdsWI
language:
Prolog (swi 7.6.4)
created:
6 years ago
visibility:
public

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