Building Parsers with Java™

2.3. Assemblies

In practice, we demand more of parsers than simply saying whether a string is a valid member of a language. As a parser recognizes a string, it is useful for the parser to react to the contents of the string and build something. The parser also needs to keep an index of how much of the string it has recognized. An Assembly object wraps a string with an index and with work areas for a parser, providing a stack and a target object to work on. For example, a parser that recognizes a data language for coffee might set the target to be a basic Coffee object. This parser could work on the target as it recognizes an input string, informing the Coffee object of the coffee attributes the string indicates.

If a parser needs to build something ...