A minimal CES framework

Before we get started on the details, we should define what minimal means.

Let's start with the two main abstractions our framework will provide: behaviors and event streams.

If you can recall from Chapter 1, What is Reactive Programming?, behaviors represent continuous, time-varying values such as time or mouse position behavior. Event streams, on the other hand, represent discrete occurrences at a point in time, T, such as a key press.

Next, we should think about what kinds of operations we would like to support. Behaviors are fairly simple, so at the very least we need to do the following:

1. Create new behaviors
2. Retrieve the current value of a behavior
3. Convert a behavior into an event stream

Event streams have more interesting logic at play and we should at least support these operations:

• Push/deliver a value down the stream
• Create a stream from a given interval
• Transform the stream with the map and filter operations
• Combine streams with flatmap
• Subscribe to a stream

This is a small subset, but big enough to demonstrate the overall architecture of a CES framework. Once we're done, we'll use it to build a simple example.