Behave

A simple implementation of behavior trees in MoonScript / Lua.

Example

(Note: The top example and last example work. The others are from experimenting with ideas about how to make it easier to write code interfacing with this library.)

bt = require "behave"

tree = bt.Sequence({
  bt.Node({
    run = function(self)
      -- do stuff
    end,
    finish = function(self)
      -- finish up
    end
  }),
  bt.Random({
    bt.Node({
      -- add some functions
    }),
    bt.Node({
      -- even more functionality!
    })
  })
})

node1 = {
  -- pretend this has run/finish functions or whatever
}
node2 = {} -- same
bt.Make ({
  "Sequence",
  node1, node2, {
    "Random",
    node3, node4 -- these are in 'Random'
  }
})

tree = bt.Factory({
  "Sequence",
  {
    "Node",
    {
      run = function(self) end,
      finish = function(self) end
    }
  }
})

node1 = bt.Node()
function node1:run()
  -- do stuff!
end

The Leaf Node

Node accepts a table of values to be set on it. It expects a run function, and optionally a start and a finish function, which will only be run at the beginning and end of a node being run (whereas run can be called multiple times).

To run a behavior tree, call update on itself, with optional arguments (which will be passed to their children as they are called).

Composite Nodes

Pass a table of nodes to these to set their contents. All composite nodes repeat after the entire tree has been processed.

• Sequence: Runs children until a failure or success of all.
• Selector: Runs children until a success or failure of all.
• Random: Runs a random child and returns its result.
• RandomSequence: Randomizes the order of its children, then acts like a Sequence.
• RandomSelector: Randomizes the order of its children, then acts like a Selector.

Decorator Nodes

Pass a single node to these, except for Repeat, which needs a number followed by a node. All decorator nodes (except RunOnce) repeat after the entire tree has been processed.

• Repeat: Repeats a node a specified number of times, fails if the node fails.
• Decorator: Does nothing except return the result of its child node.
• Succeed: Runs a node and returns success.
• Fail: Runs a node and returns failure.
• Invert: Runs a node, reporting a success on fail, and failure on success.
• RunOnce: Runs a node, reporting its results, and fail after that.

Return Values

Within the module, success, running, and fail are defined. They are also present on all nodes (so you can use self.success and such).