Interpreter

The Interpreter is simply a Composite. They have the same sructure while differs a little in motivation. As is introduced in the earlier entry, object in Composite pattern can be treated equivalently, both simple ones and complicated ones made up of simple ones. The Interpreter aims at building an interpreter for a specific language used in a compiler/interpreter (e.g. for Fortran/perl). The simple objects are those terminals while the Composites are non-terminal expressions.