Language Features for Writing DSLs

In this section, we'll look at the Scala features that make it easy to write small DSLs:

• Flexible syntax for method invocation

• By-name parameters

• Extension methods and Value classes

We'll use all of these features in the next section when we create our own DSL in Scala.

Flexible Syntax for Method Invocation

Scala has a flexible syntax for method invocations that makes it possible to, in some cases, omit the dot ( .) and parentheses ( ()) when invoking methods.

The rules are as follows:

• For methods that are of arity- 0, meaning they don't take any parameters, the parentheses can be omitted and you can use the postfix notation.

• For methods with an arity of 1 or more, meaning they take one or more parameters, it's possible to write the method using infix notation.

Here's an example of using infix notation when invoking filter:

List.range(0, 10).filter(_ > 5)
List.range(0, 10) filter (_ > 5)

And here's an example of omitting the parentheses when invoking...