Expressions, Values, and Types
With the setup complete we're ready to start learning to program! We have two goals in this chapter:
- to write and run our first Scala code; and
- to start building our model of how code works.
The first is clearly important: we won't get very far learning Scala if we cannot write and run Scala code. The second perhaps needs a bit more explanation. To learn how to program we need to learn to think about code in a number of different ways. The first way, which we're starting here, is to build a model of what happens when code runs. We say it's a model because it's not exactly what happens, but rather a very useful approximation. It will tell us some things, but not everything.
To get more specific, we start to build our model of how code works by looking at expressions and values, and the process of evaluation that connects expressions to values. We'll then talk about types, and the process of compilation that constructs them.
We are also, of course, going to write some code along the way. This is important in its own right but will also help ground our more theoretical discussion. One of the great things about programming is that we can easily test our mental models by seeing what the computer actually does.