LUA / World Of Warcraft
LUA Crib Sheet
(Last updated: Oct 1st 2006)

Console
Operators
Variables
Strings
Tables
Functions
Flow of Control
Other Items of Interest

Console

• Start main exe with -console
• Use ~ to display console
• gxWindow 0 -- Windowed mode
  gxWindow 1 -- Full screen
  gxRestart -- Apply above
   

Operators

Operation	Operator	Notes
String concatenation	..	"Hello " .. "World" ("Hello " + " World" will NOT work)
Equality	==	if (x == y)
Inequality	~=	if (x ~= y)
Not	not
<, >, <=, >=	<, >, <=, >=	Work with both numeric and string values
AND	and	AND and OR are unusual if the arguments are not boolean. x and y -- returns x if x != false, otherwise returns y x or y -- returns x if x == false (or nil), otherwise returns y This can be used to default values. For example, a = b or "default" Also, x and y or z equates to a ? b : c
OR	or
Null test	== nil

Variables

• Variables are not strongly typed. Implicit conversion is common (for example "123" + 1 is legal and returns 124).
   
• Undeclared variables and functions (including typos) have a value of nil.
   
• Variable not declared local are global to all modules and add-ins. Variables declared outside of code block are global and assigned at start up [todo confirm].
   
• Variables names in the toc file's ## SavedVariables: list are automatically saved when the UI is unloaded (i.e. the character logs out, quits or the ReloadUI function is called).
   
• Multiple assignments are allowed, but the assignment order is not guaranteed:
  x,y = 1,2 -- Assigns 1 to x and 2 to y

  x,y = MyFunction() -- Function returns two values

  x,y = y,x -- This is an exception to the rule and is guaranteed to work as hoped.

  x,x = 1,2 -- Cannot say whether x will be 1 or 2

  a,b = b,c -- Cannot say what the value of b will be

  
  
• Too many or too few right hand side args does not cause an error :
  x,y = 1,2,3 -- no error

  a,b,c = 1,2 -- c is set to nil

  
  
• 
  x,y = 1,2,3 -- no error
  a,b,c = 1,2 -- c is set to nil
   

Strings

• String deliminators supported are: ", ' and [[
   
• Strings inside [[ ]] do not escape characters.
   
• String can be split over multiple lines without concatenation characters.

Function	Description
tostring(anything)	Converts anything to a string
string.format(format, args)	Supported template chars: %s = string %d = decimal %c = char %f = floating point number (%g = compact fp number) %x = hex (%X = uppercase hec)
string.find(s1, s2)	Returns the index of s2 in s1
string.len("abcde")	Returns the string length
string.lower("ABCDE")	Converts to lowercase
string.upper("abcde")	Converts to uppercase
string.sub("abcde", from) string.sub("abcde", from, to)	Returns string subsections

• Non-trival string operations are exposed through the string class, e.g.: string.byte("abc", 2) -- Equ. ASCII('b')
   

Tables

• Closest to array and structure support is Tables which are defined using a { syntax:
  myTable = {field1 = 123, field2 = 234, myfield = "123"}

  x = myTable.field1

  x = myTable[1] -- tables are 1-based

  y = { } -- Creates an empty table

  
  
• Tables can be nested.

Function	Description
table.insert(myTable, newValue)	APPENDs newValue
table.insert(myTable, newValue)	Inserts newValue
table.insert(myTable, index, newValue)	Get the size of the table
table.getn(myTable)	Calls function for each item in the table
table.foreachi(mytable, function)	Based on the index of the item. Note the trailing 'i' on foreachi. t = {1,2,3,4,5}
table.foreach(mytable, function)	Calls function for each item in the table based on the key of the item (myTable["key"] = "123" or t = {a="1", b="2"})
table.sort(myTable, function(a,b) return a>b end)	Sorts the table using the logic in the provided function.

• t = {2,4,6} is really t= {"1"="2", "2"="4", "3"="6"}
   
• x, y, z = unpack({1,2,3})

Functions

• Functions can be assigned to variables.
  x = function() print("Hello World") end; x();
  
  
  
• Placing brackets around a function call that returns multiple values causes only the first value to be returned,
  function TwoValues()

      return 1,2;

  end

   

  x = (TwoValues()); -- x = 1

  
  

  e.g x = (myFunction(1, 20))

  Functions can be declared in two ways: function funcName(args) ... end; funcName = function(args) ... end; and args of string literial '...' indicates a variable number of arguments (which will be represented by a table called args, e.g. function(a, ...) called with (1, 2, 3, 4) would give arg[2] of 3. [TODO prove]

  
  

Flow of control

• if construct
  if expression then

      ...

  [else

      ... ]

  end;
  

  
  
• for construct
  for count = from, to [, step] do

      ...

  end;
   

  for key, value in {1, key2="value2", 3, 4} do

      ...

  end;

  
  
• while constructs
  while expressionIsTrue do

      ...

  end

   

  repeat

      ...

  until expressionIsTrue;

  
  
• case construct
  ?

  
  

  
  
• case construct
   

Other Items of interest

• LUA tutorials at http://lua-users.org/wiki/TutorialDirectory
   
• LUA Visual Studio syntax coloring: http://luaforge.net/projects/lualangpack
   
• Statement terminator is ; and is optional.
   
• String deliminators supported are: ", ' and [[. Strings inside [[ ]] do not escape characters. String can be split over multiple lines without concatination characters.
   
• Non-trival maths operations are exposed through the math class:
  math.sqrt(64) -- 8
  math.pi -- constant
  math.floor
  etc.