NekoVM

NekoVM is a virtual machine developed by Nicolas Cannasse as part of research and development (R&D) efforts at two indie video game firms in Bordeaux, France: first at Motion Twin and then at Shiro Games. NekoVM's native language is the bytecode for a high-level dynamically typed programming language called Neko. This pairing allows Neko to be used directly as an embedded scripting language or to target NekoVM by compiling some other language (such as Haxe) to NekoVM bytecode.

Neko
ParadigmObject-oriented, structured, prototype-based, scripting
Designed byNicolas Cannasse
DeveloperMotion Twin, Shiro Games
First appeared2005 (2005)
Stable release
2.3.0 / October 24, 2019 (2019-10-24)
Typing disciplineDynamic
Implementation languageC, OCaml
PlatformIA-32, x86-64
OSWindows, macOS, Linux
LicenseMIT
Filename extensions.neko .n
Websitenekovm.org
Major implementations
Neko, Haxe

Concept

Neko has a compiler and a virtual machine (VM) with garbage collection. The compiler converts a source .neko file into a bytecode .n file that can be executed with the VM. Since Neko is dynamically typed with no fixed classes, a developer only needs to find the proper runtime mapping (in contrast to type mapping) so that code executes correctly. As the Neko FAQ puts it: "...it is easier to write a new or existing language on the NekoVM than it is for the CLR / JVM, since you don’t have to deal with a highlevel type system. Also, this means that languages can interoperate more easily since they only need to share the same data structures and not always the same types."[1]

Neko requires compiling before executing, like other scripting languages such as Apache Groovy. Since Neko need not be interpreted at runtime, it executes faster. The Haxe programming language can compile to Neko code, among other targets.

Virtual machine

The Neko virtual machine is used to execute a Neko bytecode file, the VM also has the option to convert a bytecode file into an executable file (output changes depending on the target operating system).

Examples

Hello World

 
$print("Hello World!");

Type conversions

 
$int("67.87"); // Converts string "67.87" to integer 67
$float(12345); // Converts integer 12345 to float 12345.0000
$string($array(1,2,3)); // Converts array [1,2,3] to string "[1,2,3]"

Objects

 
o = $new(null); // new empty object
o2 = $new(o); // makes a copy of o
o2 = $new(33); // if parameter is not an object, throw an exception
o.field = value; //sets field to value
o.field; // returns "field" value of object o

Methods

 
foo = function() {
	$print(this.x);
}
o = $new(null);
o.x = 3;
o.bar = function() { 
	foo(); 
};
o.bar(); // prints 3

Function scope

 
var x = 3;
f = function() {
	$print(x);
}
x = 4;
f(); // print 3

Prototypes

 
var proto = $new(null);
proto.foo = function() { 
  $print(this.msg) 
}

var o = $new(null);
o.msg = "hello";
$objsetproto(o,proto);
o.foo(); // print "hello"

$objsetproto(o,null); // remove proto
o.foo(); // exception

Web functionality

Neko includes a mod_neko module for the Apache server. As such, it can process user input using GET and POST requests:

get_params = $loader.loadprim("mod_neko@get_params",0);
$print("PARAMS = "+get_params());

See also

References
  1. "How is Neko different from .Net's CLR or the Java's JVM ?". Neko FAQ. Retrieved 9 January 2011.
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