Courses/CS 460/Fall 2005/Homework/Duc Trinh/Oct 1

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Contents 1 Homework 1 1.1 InTheList 1.2 GetElementUpToIndex 1.3 GetSumOfElements and GetAverage

[edit] Homework 1

Comments / Notes / Questions:

• All my examples are for list. I couldn't figure out the binary tree.

[edit] InTheList

% returns a yes if a specified element is in the list
declare fun {InTheList List A B}
	   case List of H|T then
	      if (H==A) then
		 B=yes
	      else if T \= nil then
		      {InTheList T A B}
		   else
		      B=no
		   end
	      end
	   end
	end

local List1 X Y in
   List1 = [1 2 3 4 5 6]
   X = 6
   {Browse {InTheList List1 X Y}}
end

[edit] GetElementUpToIndex

% Return a list up to a specified index from the original list.
declare fun {GetElementUpToIndex List3 Index}
	   case List3 of H|T then
	      if (Index > 0) then
		 H | {GetElementUpToIndex T Index-1}
	      else
		 nil
	      end
           [] nil then nil
	   end
	end

local X in
   X = [11 2 3 38 99 37 38 22]
   {Browse {GetElementUpToIndex X 4}}
   end

[edit] GetSumOfElements and GetAverage

% Get the sum of elements in a list consisting of numbers only.

declare fun {GetSumOfElements List}
	   case List of H|T then
	      if T \= nil then
		      H + {GetSumOfElements T} 
	      else
		      H
	      end
	   end
	end

% Get the average for elements in a list consisting of numbers only.

declare fun {GetAverage List2}
	   {GetSumOfElements List2} div {Length List2}
	end
		 
local X in
   X = [11 2 3 38 99 37 38 22]
   {Browse {GetSumOfElements X}}
   {Browse {GetAverage X}}
   end

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