Haxe is a high-level cross-platform programming language and compiler that can produce applications and source code for many different computing platforms from one code-base. It is free and open-source software, released under the MIT License. The compiler, written in OCaml, is released under the GNU General Public License (GPL) version 2.
Haxe includes a set of features and a standard library supported across all platforms, like numeric data types, strings, arrays, maps, binary, reflection, maths, Hypertext Transfer Protocol (HTTP), file system and common file formats. Haxe also includes platform-specific API's for each compiler target. Kha, OpenFL and Heaps.io are popular Haxe frameworks that enable creating multi-platform content from one codebase.
Haxe originated with the idea of supporting client-side and server-side programming in one language, and simplifying the communication logic between them. Code written in the Haxe language can be compiled into JavaScript, C++, Java, JVM, PHP, C#, Python, Lua and Node.js. Haxe can also directly compile SWF, HashLink, and NekoVM bytecode and also runs in interpreted mode.
Haxe supports externs (definition files) that can contain type information of existing libraries to describe target-specific interaction in a type-safe manner, like C++ header files can describe the structure of existing object files. This enables to use the values defined in the files as if they were statically typed Haxe entities. Beside externs, other solutions exist to access each platform's native capabilities.
Many popular IDEs and source code editors have support available for Haxe development. No particular development environment or tool set is officially recommended by the Haxe Foundation, although VS Code, IntelliJ IDEA and HaxeDevelop have the most support for Haxe development. The core functionalities of syntax highlighting, code completion, refactoring, debugging, etc. are available to various degrees.
History
Development of Haxe began in October 2005. The first alpha version was released on November 14, 2005. Haxe 1.0 was released in April 2006, with support for Adobe Flash, JavaScript, and NekoVM programs. Support for PHP was added in 2008, and C++ was added in 2009. More platforms such as C# and Java were added with a compiler overhaul in 2012.
Haxe was developed by Nicolas Cannasse and other contributors, and was originally named haXe because it was short, simple, and "has an X inside", which the author asserts humorously is needed to make any new technology a success.
Haxe is the successor to the open-source ActionScript 2 compiler MTASC, also built by Nicolas Cannasse and is released under the GNU General Public License version 2 or later.
Compiler
The Haxe language can compile into bytecode that can be executed directly by the virtual machines it targets. It can compile to source code in C++, JavaScript, PHP, C#, Java, Python, and Lua. Haxe also has an interpreter called eval. This same interpreter is also used compile-time to run macros, which allow modification of the abstract syntax tree (AST).
This strategy of compiling to multiple source code languages is inspired by the write once, run anywhere paradigm. It also allows the programmer to choose the best platform for the job. Typical Haxe programs run identically on all platforms, but developers can specify platform-specific code and use conditional compilation to prevent it from compiling on other platforms.
The Haxe compiler is an optimizing compiler, and uses field and function inlining, tail recursion elimination, constant folding, loop unrolling and dead code elimination (DCE) to optimize the run-time performance of compiled programs. The Haxe compiler offers opt-in null-safety, it checks compile-time for nullable values.
Targets
In Haxe, supported platforms are known as "targets", which consist of the following modules: The compiler-backends that are responsible for generating the respective code. The run-time specific APIs that go beyond the core language support (platform-targets).
The following table documents platform and language support in Haxe. The Haxe language allows developers to gain access to many platform features, but Haxe is not a full featured engine, they might need frameworks that enable create content for certain platforms.