CS-460-1.Fall-2005:Homeworks:JayDonnellHomework

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[edit] Homework 1

% Get the last element of a list manually. This is just to practice manipulating lists without builtins

local Last ListIn Element in

   ListIn = [1 2 3]

   proc {Last ListIn ?Element}
      case ListIn of Head|Tail then
	 if Tail == nil then
	    Element = Head
	 else
	    {Last Tail Element}
	 end
      end
   end
   {Last ListIn Element}{Browse Element}

end

% Reverse a list manually. 
local Rev ListIn ListOut in

   ListIn = [1 2 3]
   
   proc {Rev ListIn ?ListOut}
      local L Laste Result NewLength ShortList in
         if ListIn == nil then ListOut = nil
         else

	   {Length ListIn L}
	   {Number.'-' L 1 NewLength}
	   if L == 1 then
	      ShortList = nil
	      {List.last ListIn Laste}
	   else
	      {List.take ListIn NewLength ShortList}
	      {List.last ListIn Laste}
	   end
	   {Rev ShortList Result}
           ListOut = Laste|Result
   
         end
      end
   end
   
   {Rev ListIn ListOut} {Browse ListOut}

end

% Find the max element of a tree

local Insert T T2 T3 T4 TMax Out in
   
proc {Insert Key Value TreeIn ?TreeOut}
   case TreeIn
   of nil then TreeOut = tree(Key Value nil nil)
   [] tree(K1 V1 T1 T2) then 
      if Key == K1 then TreeOut = tree(Key Value T1 T2)
      elseif Key < K1 then T in 
        TreeOut = tree(K1 V1 T T2)
        {Insert Key Value T1 T}
      else T in 
        TreeOut = tree(K1 V1 T1 T)
        {Insert Key Value T2 T}
      end 
   end 
end

proc {TMax Tr ?V}
   {Browse 'in find'}
   case Tr
   of nil then V = nil
   [] tree(K1 V1 T1 T2) then
      if T2 == nil then V = V1
      else
	 {TMax T2 V}
      end
   end
end

T = nil
{Insert 9 'jay' T T2}
{Insert 3 'bob' T2 T3}
{Insert 13 'zed' T2 T4}
{Browse T4}
{TMax T4 Out}
{Browse 'out'}
{Browse Out}
end

% Search a tree by key

local Insert T T2 T3 Find Out in
   
proc {Insert Key Value TreeIn ?TreeOut}
   case TreeIn
   of nil then TreeOut = tree(Key Value nil nil)
   [] tree(K1 V1 T1 T2) then 
      if Key == K1 then TreeOut = tree(Key Value T1 T2)
      elseif Key < K1 then T in 
        TreeOut = tree(K1 V1 T T2)
        {Insert Key Value T1 T}
      else T in 
        TreeOut = tree(K1 V1 T1 T)
        {Insert Key Value T2 T}
      end 
   end 
end

proc {Find Tr K V}
   {Browse 'in find'}
   case Tr
   of nil then V = nil
   [] tree(K1 V1 T1 T2) then
      if K == K1 then V = V1
      elseif K < K1 then
	 {Find T1 K V}
      else
	 {Find T2 K V}
      end
   end
end

T = nil
{Insert 9 'jay' T T2}
{Insert 3 'bob' T2 T3}
{Browse T3}
{Find T3 3 Out}
{Browse 'out'}
{Browse Out}
end