Learning experiment for designing a prototypal programming language
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Eve 0.3.5

An experiment to learn how to make an interpreter.
Eve is a simple interpreted language that targets the JVM.


Eve is a dynamically strongly typed, pure prototypal, object-oriented language:

  • Everything is an object, and there are no classes.
  • Objects are generated by cloning prototypes and existing objects.
  • Objects have no delegation relationship with one another (as in JavaScript); this reduces confusion and mistakes when dealing with references.
  • Eve runs on the Java Virtual Machine, and integration with Java code is possible.

For more information about prototypal OOP programming, see the Wikipedia article:



First, write an eve file. See the wiki for language reference, tutorials, and examples. Then, invoke the Eve interpreter:

java -jar dist/eve.jar file.eve

You can invoke the executable jar with the -h option to get more a summary of options used to tweak the interpreter.


First, check out the code from the Git repository. The master branch always reflects the latest stable release, while develop reflects the latest code under development.

The primary requirement for building and running Eve is Java. Eve is developed and tested on the "official" 1.6 HotSpot VM. It should work under Java 1.5, but that environment is unsupported. It will not work under Java 1.4 or lower.

Eve uses Apache Ant for building and Apache Ivy for resolving dependencies. Make sure to install those first. On Linux, your distro may have them. For example, to install Ant and Ivy on Ubuntu 10.10:

sudo apt-get install ant ivy

If necessary, install Ant and Ivy manually. They can be found at:


Once having installed Ant and Ivy and putting them on your classpath, run the build script by typing "ant" in the root of the repository. Dependencies will be fetched and added to the classpath automatically.

The build process will produce an executable jar eve.jar in the dist directory. Execute java -jar dist/eve.jar to start the interpreter.


Starting with 0.3.4, there is now a task in the build.xml file that will install eve to /usr/local/ on Unix machines. Run sudo ant install (or equivalent) and you will have /usr/local/bin/eve. This allows eve to be executed more naturally:

eve file.eve


If you want to run the test suite, run ant test instead of ant jar.


Building Issues

Before running Ant, make sure Ivy is on your classpath. If Ivy is not on the classpath, the dependecy resolution task will fail. For example, to get Ivy on the classpath in Ubuntu 10.10:

export CLASSPATH=/usr/share/java/ivy.jar:$CLASSPATH

Interpreter Can't Find Dependencies

The executable jar requires a number of dependencies. Make sure a lib/ directory exists in the location where eve.jar is, and make sure all required dependencies are in that directory. If those are present, Eve should able to be run from anywhere. The build process should dump all required dependencies into the dist/ directory for you.

Release Notes


  • typedef statement.
  • Significant rework of how built-in types and standard library is loaded.
  • Much smoother support for creating "native code" through the use of annotations.
  • Rewrote native namespaces (now known as modules) using new annotations.
  • Renamed java namespace to eji since it conflicted with the java built-in type.
  • Significant enhancements to the import function:
    • EJI import standard namespace by namespace name (e.g. import("eji"))
    • EJI import type by package:type (e.g. import("com.mycompany:mynamespace"))
    • EJI import type namespace by class name (e.g. import("com.mycompany.MyNamespace"))
  • Completely removed namespaces in favor of typedef:
    • All "namespaces" are now actually types (that cannot be created).
    • :: operator repurposed to do property resolution on types.
    • Invocation of namespace functions basically remain unchanged (e.g. "eji::import" still works).
    • Namespaces are now more properly known as module types.
    • Every script is executed in the global scope.
  • Scope blocks:
    • Added scope(private) and scope(global) to force scope changes.
    • scope(private) isolates code inside it from the outside world.
    • scope(global) allows block to resolve variables in the global scope.


  • Basic REPL.
  • Reference equality operators === and !==.
  • "Equals Expressions": +=, -=, etc.
  • Unix install task: will install to /usr/local/lib/eve/. No task for Windows yet.


  • Fixed null pointer exception related to auto deep cloning with closures.


  • Put release notes in the readme file!
  • Added automatic deep cloning for lists and dicts.
  • Changed def and delegate syntax to be less obtuse.
  • Added null value and variable initialization without assignment.


  • Bug fixes of some sort.


  • Large update that completely changes how to create objects.

Big things left to do:

  • Object family support (for pushing changes to many objects)
  • Ahead of Time "compilation"
  • A standard library

Things to consider:

  • Multithreading