In modern programming, we sometimes have to deal with problems from well-understood and well-defined domains. In some cases, it makes sense to represent the domain with a language, which could then make it easy to solve problems using an interpreter. This is exactly what the interpreter design pattern is useful for:
It specifies how to evaluate sentences in a language by representing it using classes and building syntax trees to evaluate the language expressions.
The interpreter design pattern makes use of the composite design pattern as well. Some common uses of interpreters are for language parsing, protocols, and so on.
Creating a language and grammar is a complicated task and before getting into ...