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185 lines
6.7 KiB
OCaml
185 lines
6.7 KiB
OCaml
(*
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Copyright (c) 2013, Simon Cruanes
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer. Redistributions in binary
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form must reproduce the above copyright notice, this list of conditions and the
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following disclaimer in the documentation and/or other materials provided with
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the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*)
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(** {1 Behavior Trees for React} *)
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(** Behavior trees are a modular alternative to state machines for controlling
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dynamic behavior in time. They are primarily used in video games to
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implement non-player AI.
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A tree is composed of basic actions, basic tests, and combinators. During
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execution, some subset of the nodes of a tree may be {b running}; at some
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point the execution of a given node will terminate with either
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{b success} or {b failure}. Depending on the kind of node, this result
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may propagate to parent nodes, or set other nodes running.
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For instance, a {i sequence} node runs its subtrees one by one. If a
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subtree succeeds, the next one is activated; if it fails, the whole
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sequence will fail.
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Here, we build them on top of
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{{: http://erratique.ch/software/react/doc/React.html} React}.
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Documentation source:
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{{: http://aigamedev.com/open/article/bt-overview/} aigamedev (and links)}
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*)
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(** {2 Behavior tree} *)
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type tree = private
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| Test of bool React.event (* test the next occurrence *)
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| TestFun of (unit -> bool) (* call and test value *)
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| Wait of unit React.event (* wait for the event to trigger *)
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| Timeout of float (* fails after the given timeout *)
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| Do of (unit -> bool) (* perform an action *)
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| If of bool React.signal * tree * tree (* switch *)
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| Sequence of bool * tree list (* yield to subtrees sequentially. bool: loop? *)
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| Select of select_strategy * tree list (* select one subtree *)
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| Parallel of parallel_strategy * tree list (* run all subtrees in parallel *)
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| Closure of (unit -> tree) (* build a tree dynamically *)
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| Succeed
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| Fail
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(** A behavior tree *)
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and select_strategy = tree list -> (unit -> tree option)
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(** How to select a subtree to run. It may yield a different result each
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time it is called. *)
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and parallel_strategy =
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| PSForall (** succeeds when all subtrees succeed *)
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| PSExists (** succeeds when some subtree succeeds (kill the others) *)
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val strategy_inorder : select_strategy
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(** Select subnodes one after the other, then fails *)
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val strategy_random : ?proba_fail:float -> select_strategy
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(** Randomly chooses a subtree. May fail at each point with
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a probability of [proba_fail]. *)
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val succeed : tree
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(** Behavior that always succeeds *)
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val fail : tree
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(** Behavior that always fails *)
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val test : bool React.event -> tree
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(** Fails or succeeds based on the next occurrence of the event *)
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val test_fun : (unit -> bool) -> tree
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(** Tests that the result of calling this function is true *)
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val test_signal : bool React.signal -> tree
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(** Fails or succeeds based on the current signal value *)
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val wait : unit React.event -> tree
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(** Wait for the event to trigger, then succeed *)
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val timeout : float -> tree
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(** Fails after the given amount of seconds *)
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val delay : float -> tree
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(** Wait for the given amount of seconds, then succeed *)
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val do_ : (unit -> bool) -> tree
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(** Perform an action, then succeed iff it returned true *)
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val do_succeed : (unit -> unit) -> tree
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(** Perform an action and succeed (unless it raises an exception) *)
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val if_ : bool React.signal -> tree -> tree -> tree
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(** Conditional choice, based on the current value of the signal *)
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val sequence : ?loop:bool -> tree list -> tree
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(** Sequence of sub-trees to run *)
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val select : ?strat:select_strategy -> tree list -> tree
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(** Choice among the subtrees. The strategy defines in which order subtrees
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are tried. *)
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val or_else : tree -> tree -> tree
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(** Binary choice, favoring the left one *)
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val parallel : ?strat:parallel_strategy -> tree list -> tree
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(** Run subtrees in parallel (default strat: PSForall) *)
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val closure : (unit -> tree) -> tree
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(** Produce a tree dynamically, at each call. *)
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(** {2 Lightweight futures} *)
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module Fut : sig
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type 'a t
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(** Future value of type 'a *)
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val create : unit -> 'a t * ('a -> unit)
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(** Create a future, and a function that sets its value (if already set,
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will raise Invalid_argument) *)
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val subscribe : 'a t -> ('a -> unit) -> unit
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(** Get notified exactly once with the value (maybe right now) *)
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val is_set : 'a t -> bool
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(** Value already known? *)
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val return : 'a -> 'a t
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(** Monadic return (returns immediately) *)
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val bind : 'a t -> ('a -> 'b t) -> 'b t
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(** Monadic bind *)
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val next : 'a React.event -> 'a t
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(** Next occurrence of the event *)
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val wait : 'a t -> 'a option React.signal
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(** The value of the future (None while it's not set) *)
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val map : ('a -> 'b) -> 'a t -> 'b t
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(** Simple map *)
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val first : 'a t list -> 'a t
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(** First future of the list to be set (or any that is already
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set if at least one is set) *)
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val last : 'a t list -> 'a t
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(** Last future to be set (or any if they are all already set) *)
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val filter : ('a -> bool) -> 'a t list -> 'a option t
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(** Filters out results that do not satisfy the predicate; returns the
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first result that satisfy it, or None *)
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val l2 : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t
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(** Binary lift *)
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end
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(** {2 Run a tree} *)
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type result = bool Fut.t
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val run : ?delay:(float -> unit React.event) ->
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tree ->
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result
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(** Run the tree. It returns a {! result}, which wraps
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either true (success) or false (failure).
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[delay] is the function to call to get notified after the given amount of
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seconds elapsed. *)
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