Beehave 
A simple library for defining and evaluating a hierarchical state machine (behaviour tree).
Documentation
Compatibility
Because this library uses fn_traits and unboxed_closures it will only compile using rust nightly.
See rust-lang/rust#29625 for the related issue around stabilization.
This was last tested against rustc 1.13.0-nightly (a23064af5 2016-08-27)
Example
Building a behaviour tree using the supplied macros:
```rust
let worldbehaviour: Selector = behaviourselector!("World Root", [
condition!("Ensure Can Shine",
|world: &mut World| {
world.canshine()
},
action!("Cycle Day/Night", |world: &mut World| {
world.togglesun()
})
),
condition!("Ensure Can Rain",
|world: &mut World| {
world.can_rain()
},
action!("Rain", |world: &mut World| {
world.rain()
})
)
]);
let treebehaviour: Selector = behaviourselector!("Tree Root", [
behavioursequence!("Photosynthesise", [
condition!("Ensure Can Make Energy",
|tree: &mut Tree| {
tree.canmakeenergy()
},
action!("Make Energy", |tree: &mut Tree| {
tree.makeenergy()
})
),
condition!("Ensure Can Grow",
|tree: &mut Tree| {
tree.cangrow()
},
action!("Grow", |tree: &mut Tree| {
tree.grow()
})
),
condition!("Ensure Can Emit Oxygen",
|tree: &mut Tree| {
tree.canemitoxygen()
},
action!("Emit Oxygen", |tree: &mut Tree| {
tree.emitoxygen()
})
)
]),
condition!("Ensure Can Gather Sun",
|tree: &mut Tree| {
tree.cangathersun()
},
action!("Emit Oxygen", |tree: &mut Tree| {
tree.gathersun()
})
),
condition!("Ensure Can Gather Water",
|tree: &mut Tree| {
tree.cangatherwater()
},
action!("Emit Oxygen", |tree: &mut Tree| {
tree.gatherwater()
})
)
]);
```
Evaluating the behaviour tree against an actor:
rust
tree_behaviour.evaluate(&mut tree);
world_behaviour.evaluate(&mut world);
For more information please see the full example.
You can run the example using:
sh
cargo run --example main
Design Goals
- Easily generate an immutable behaviour tree
- Evaluate the behaviour tree on a mutable actor
See also
PistonDevelopers/ai_behavior
License
Beehave was created by Ryan Scott is distributed under the MIT license.