Last modified on 21 March 2012, at 15:35

Monkey/Language/Lists

What are Lists?Edit

In Monkey, lists are a set of objects that are encapsulated in an object, and read in a set sequential order. Lists have the power to be read forwards, backwards, traversed object-by-object, sorted, and offer a node-level access for insertion and queries.

Example:

Class Obj
	Field x:Int, y:Int, z:Int
 
	Method New(xx:Int,yy:Int,zz:Int)
		x=xx; y=yy; z=zz
	End
End
 
Function Main()
	mylist = New List<Obj>
	mylist.AddLast(New Obj(1,1,1))
	mylist.AddLast(New Obj(2,2,2))
	mylist.AddFirst(New Obj(3,3,3))
 
	Print "list:"
 
	For Local o:Obj = Eachin mylist
		Print o.x+" "+o.y+" "+o.z
	Next
End

A list is created like any other object with the 'NEW' keyword. It differs from other objects because it requires a type specifier. Type specifiers (or type parameters) are defined using the greater than-less than signs: < and >. In the above example, the list 'mylist' is a list of 'Obj's, which is a class of three fields: x, y, and z.

'EachIn' will automatically iterate through a list, assigning the object to the iterating variable. EachIn will exit the loop when a NULL is reached, signaling the end of the list.


What are Nodes?Edit

Syntax for a list's node:

Local mynode:list.Node<Obj>
mynode = mylist.FirstNode()


Nodes are also created when an object is added to a list:

Local mynode:list.Node<Obj> = mylist.AddLast(New Obj(4,4,4))


Nodes can return a value from the list:

Local o:Obj = mynode.Value()
 
Print o.x+" "+o.y+" "+o.z


Nodes can be used to iterate through a list backwards:

Local  mynode:list.Node<Obj> = mylist.LastNode()
 
While mynode
	Local o:Obj
	o = mynode.Value()
 
	Print o.x+" "+o.y+" "+o.z
 
	mynode = mynode.PrevNode() 
Wend


Nodes can insert a value into a list, using the Node constructor (the New command):

Local  mynode:list.Node<Obj> = mylist.FirstNode()
Local insertdata:Obj = New Obj(9,9,9)
 
While mynode	
	If mynode.Value.x = 2
		''insert after
		New list.Node<Obj>(  mynode.NextNode(), mynode, insertdata)
	Endif
 
	mynode = mynode.NextNode() 
Wend


Nodes can remove a value from a list, although be sure to be done with that node before you remove it:

Local  mynode:list.Node<Obj> = mylist.FirstNode()
Local  removenode:list.Node<Obj>
 
While mynode	
	If mynode.Value.x = 2
		''remove
		removenode = mynode
	Endif
 
	mynode = mynode.NextNode()
	removenode.Remove()
Wend