LuaAI

A page containing information on configuring the AI using Lua. NB: previous contents of the page moved to http://wiki.wesnoth.org/LuaAI(old)

Aspects

Patch r49721 enabled users to write aspects using Lua. This simplifies the definition of aspects that are meant to change depending on the game state. A good example could be aggression, which changes depending on the time of the day(since ToD affects the actual battle performance of your forces).
Static aggression:

[aspect]
	id="aggression"
	engine="lua"
	value="0.3"
[/aspect]

Dynamic aggression:

[aspect]
	id=aggression
	engine=lua
	     
	code=<<
		wesnoth.fire("store_time_of_day")
		local value = 0
		tod = tostring(wesnoth.get_variable('time_of_day').name) 
		if (tod == 'Morning') then
			value = 0.2
		else
			value = 1
		end
	
		wesnoth.fire("clear_variable", {name = "time_of_day"})
		return value
	>>      
[/aspect]

Note: the way of getting the ToD is hacky here, but I will create a more elegant method soon(Nephro).
Also note the difference between 'code' and 'value' attributes, this is important.

At the moment, it is possible to create the following aspects using Lua(the list will be constantly updated):

aggression          // double
attack_depth        // int
caution             // double
leader_aggression   // double
leader_value        // double

Note: simple numeric, bool and string aspect creation can be enabled just by adding a specific factory to registry.cpp, this will also soon be done.