.NET Design Patterns

The expression evaluator and interpreter pattern

The authors of this book believe that any programmer worth his salt needs to learn the rudiments of compiler construction for implementing mini-languages or domain-specific language (DSL) in his work. A compiler treats expressions as data, and expressions are mostly hierarchical in nature. We use a data structure called AST for representing the nodes of an expression tree. To convert textual expressions into an AST, we need to write a parser to analyze the constituents of an expression. The subsystem which feeds data to the parser is a module called lexical analyzer, which breaks the input stream into a series of tokens.

The definition of a mini language, and writing an evaluator for it, is dealt ...