This was originally asked for on the mailing list:
> From: romeo kalebic <romeo.kalebic@k...> > > I'm learning lua with small fsm machine built in C and all actions are > built in lua. > FSM is described with: old_state, event, new_state and action. > > state1, event1, state2, action1 > state1, event2, state3, action2 > etc.. > > Now, I like to describe fsm in lua, maybe in lua table or ?.
One easy way to do this in Lua would be to create a table in exactly the form above:
fsm = FSM{
{state1, event1, state2, action1},
{state1, event2, state3, action2},
...
}
where FSM is a function to be described soon.
Then, to run the machine, do something like this in a loop:
local a = fsm[state][event]
a.action()
state = a.new
plus some error checking if needed (eg, if a is nil, then the transition (state, event) is invalid). Also, you might want to do a.action(state, event, a.new)} if the action can use this info.
The function FSM takes the simple syntax above and creates tables for (state, event) pairs with fields (action, new):
function FSM(t) local a = {} for _,v in ipairs(t) do local old, event, new, action = v[1], v[2], v[3], v[4] if a[old] == nil then a[old] = {} end a[old][event] = {new = new, action = action} end return a end
Note that this scheme works for states and events of any type: number, string, functions, tables, anything. Such is the power of associate arrays.
Have fun. --LuizHenriqueDeFigueiredo
running version:
function action1()
print("action1")
end
function action2()
print("action2")
end
function FSM(t)
local a = {}
for _,v in ipairs(t) do
local old, event, new, action = v[1], v[2], v[3], v[4]
if a[old] == nil then a[old] = {} end
a[old][event] = {new = new, action = action}
end
return a
end
fsm = FSM{
{"state1", "event1", "state2", action1},
{"state1", "event2", "state3", action2},
}
local a = fsm["state1"]["event1"]
a.action()
state = a.new
Note: above code is Lua 5.0 and 5.1 compatible.