Editing Interpreter pattern (section)

===What solution does the Interpreter design pattern describe?===
* Define a grammar for a simple language by defining an <code>Expression</code> class hierarchy and implementing an <code>interpret()</code> operation.
* Represent a sentence in the language by an abstract syntax tree (AST) made up of <code>Expression</code> instances.
* Interpret a sentence by calling <code>interpret()</code> on the AST.

The expression objects are composed recursively into a composite/tree structure that is called
''abstract syntax tree'' (see [[Composite pattern]]).
<br>The Interpreter pattern doesn't describe how
to build an abstract syntax tree. This can
be done either manually by a client or automatically by a [[parser]].

See also the UML class and object diagram below.