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Lightweight C++ Hierarchical Task Network (HTN) AI Engine
C++ Objective-C++ Other
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Inductor Hierarchical Task Network Engine

This lightweight Hierarchical Task Network engine was first used in production in an iPhone strategy game called Exospecies. Visit the Exospecies Blog for more details. It is designed to be small, memory constrained, and used as an implementation detail of an app. It used the classic SHOP Planner as inspiration and largely followed that model.

Use and enjoy!

To Build

indhtn is designed to be built with CMake like this:

  1. Install CMake on your machine
  2. Go to the root of the indprolog repository and create a build directory. unix: mkdir build win: md build
  3. Change to that directory. unix and win: cd build
  4. CMake can build different types of projects using "generators". Run cmake -help to get a list of generators on your system: unix and win: cmake -help
  5. Pick the generator that will create the type of project you want and use the -G option to choose it. Here are the ones that have been tested: Mac make file: cmake -G "Unix Makefiles" ../src Mac Xcode: cmake -G "Xcode" ../src Windows Visual Studio: cmake -G "Visual Studio 16 2019" ../src
  6. Then actually do the build using this command which magically builds whatever you choose on the command line: cmake --build ./ 5a. OR you can manually use the build system that got created by cmake: unix or mac make file: make Mac Xcode: Open the IndProlog.xcodeproj file in the build directory using Xcode. Windows Visual Studio: Open the .sln file in the build directory using VS.

Running Tests to make sure the build worked

If you're using a command line generator of some sort, just run runtests on the commandline in your operating system of choice.


In Xcode, after you build you should change the scheme to runtests and then choose Product/Run. The output of the test will appear in the Output window.

Visual Studio

Set the default project to runtests and hit F5. You'll get a console window with the results

Directory Structure

99.99% of the code for the Htn is platform agnostic (or at least should be). It has been built and tested on Windows, Mac and iOS. The platform specific code is located in the iOS and Win directorys and is currently only a single function for debug logging.

  • /FXPlatform: Contains some general purpose code for tracing, asserts, strings, etc

  • /FXPlatform/Parser: The Inductor Parser code

  • /FXPlatform/iOS: Code specific to iOS and Mac

  • /FXPlatform/Win: Code specific to Windows

  • /FXPlatform/Prolog: The prolog compiler and runtime engine

  • /UnitTest++: The UnitTest++ framework used to write unit tests (

  • /Tests: Basic smoke tests used to make sure it compiled properly

Getting Started

Read for a tutorial on how to use InductorHTN.


Do what you like, with no warranties! Read

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