Introducing DSLs in Scala

Domain specific language (DSL) is usually useful to simplify the interaction with a system by being applied to a small particular domain. They can be targeted to programmers by providing a simplified API to communicate with a system; or they may concern the so-called "business users" who may understand a domain well enough to create some scripts but are not programmers and could have difficulty dealing with a general-purpose programming language. There are, in general, two types of DSLs:

• Internal DSLs

• External DSLs

Observing internal DSLs

Internal DSLs use a host language (for instance, Scala) and the simplified usage is obtained by adding some syntactic sugar, through tricks and special constructs of the language. The book DSLs in Action by Debasish Ghosh illustrates the construction of Scala internal DSLs using features of the language such as infix notation and implicit conversions.

He has given the following DSL usage example that represents an executable program...