Simple queue implementation in lua

Ailish

When I started writing stuff in mudlet I realized that the utter lack of anything resembling proper data types in lua is problematic.  

I wrote this simple queue implemention to simplify keeping things in a queue.  I don't know if this will be useful to anyone, but I thought I'd share.

To create a new queue, do 

your_queue=SimpleQueue:create()

to add items to the queue, do your_queue:add("some value")

to peek (look at the top element on the queue), do value=your_queue:peek()

to pop (get the top element in the queue and remove it from the queue) do value=your_queue:pop()

to get the number of items in the queue, your_queue:count()

Please let me know if this is helpful to anyone, as I plan implementing other data types.

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE MudletPackage>

<MudletPackage version="1.0">

    <ScriptPackage>

        <Script isActive="yes" isFolder="no">

            <name>Queue</name>

            <packageName></packageName>

            <script>

SimpleQueue={}

SimpleQueue.__index=SimpleQueue

function SimpleQueue:create()

  local queue={}

  setmetatable(queue, SimpleQueue)

  queue.__data__={}

  queue.__count__=0

  return queue

end

function SimpleQueue:add(value)

  table.insert(self.__data__,value)

  self.__count__=self.__count__+1

end

function SimpleQueue:peek()

if self.__count__ &gt; 0 then

return self.__data__[1]

else

return nil

end

end

function SimpleQueue:pop()

if self.__count__ &gt; 0 then 

local value=self.__data__[1]

table.remove(self.__data__,1)

self.__count__=self.__count__-1

return value

else

return nil

end

end

function SimpleQueue:count()

return self.__count__

end

</script>

            <eventHandlerList/>

        </Script>

    </ScriptPackage>

</MudletPackage>

Ailish

Since at least one person found this useful, here's also an implementation of a binary search tree (I'm not totally sure what possible use a BST could have in imperian programming, but apparently my imagination isn't good enough)

Node={}

Node.__index=Node

function Node:create()

  local node={}

  setmetatable(node, Node)

  node.key=nil

  node.data=nil

  node.parent=nil

  node.left=nil

  node.right=nil

  return node

end

BSTree={}

BSTree.__index=BSTree

function BSTree:create()

local tree={}

setmetatable(tree,BSTree)

   tree.root=nil

return tree

end

function BSTree:add(key, value)

n=Node:create()

n.key=key

n.data=value

if self.root==nil then

self.root=n

else

insertNode(self.root,n)

end 

return n

end

function BSTree:get(key)

if self.root.key==key then

return self.root.data

else

return findNode(self.root, key).data

end

end

function BSTree:delete(key)

local n = findNode(self.root,key)

if n==nil then 

return nil

end

if n.left == nil and n.right == nil then

local p = n.parent

if p.left == n then

p.left = nil

else 

p.right = nil

end

elseif n.left == nil or n.right == nil then

local c 

if n.left == nil then

c = n.right

else 

c = n.left

end

local p = n.parent

c.parent=p

if p.left == n then

p.left = c

else

p.right=c

end

else

local t_key=n.right.key

local t_data=n.right.data

self:delete(t_key)

n.key=t_key

n.data=t_data

end

end

function insertNode(tree,n)

if n.key < tree.key then

if tree.left==nil then

tree.left=n

n.parent=tree

else

insertNode(tree.left,n)

end

else

if tree.right==nil then

tree.right=n

n.parent=tree

else

insertNode(tree.right,n)

end

end

end

function findNode(tree, key)

if key == tree.key then

return tree

elseif key < tree.key then

if tree.left == nil then

return nil

elseif tree.left.key == key then

return tree.left

else

return findNode(tree.left, key)

end

else

if tree.right == nil then

return nil

elseif tree.right.key == key then 

return tree.right

else

return findNode(tree.right, key)

end

end

end

function test_tree()

ttest=BSTree:create()

ttest:add(4,"four")

ttest:add(2,"two")

ttest:add(3,"three")

ttest:add(8,"eight")

ttest:add(9,"nine")

ttest:add(6,"six")

ttest:add(7,"seven")

ttest:add(22,"twenty two")

end