echo

Using

If you're just wanting to use echo to build something there is a rather informal tutorial and a documentation for the various types and functions here. The remainder of this document will mainly deal with working on the echo source code.

Building

The framework uses buildr for building. If you haven't used this before it is a ruby tool for building JVM languages. To build the project simply do:

buildr

This will compile the project into target/classes and run all tests. You can also package echo as a jar by doing:

buildr package

There are a few other tasks added to buildfile:

• docs - builds the documentation for the source code.
• console - this builds everything then fires up a scala console with the built classes included in the classpath.

You can also use standard buildr commands to work with echo in various IDEs. These are documented here.

Hacking

Please feel free to hack on the echo source: Fork it, hack it then make a pull request.

Packages

The echo framework currently has four packages:

• root - contains EchoApp and Echo class.
• core - contains implementation of core FRP types and operations
• ui - simple UI framework classes
• io - currently contains network classes and code to deal with exceptions

Testing

Testing for echo is written using Specs. The tests are contained in src/spec/scala and are part of the core.test package so they can access package level function of FRP types. To run the tests you can simply do:

buildr test

Remember: tests are good. You should write them.

FRP Block

Much of the code in echo is implemented with respect to the original semantics of FRP. This means that many of the operations are restricted so they can only be executed during the 'setup' phase of an Echo application (see tutorial here) as otherwise they exhibit unusual behaviour. Any member functions of FRP types or functions that operate on FRP types should most likely have their code executed in an FRP block like so:

frp {
  //code
}

This allows you to guarantee that you code will only ever execute on empty Events at time 0. Of course you may be able to argue that their are use cases for an operation outside of these restrictions and if so fair enough: argue it!