This is a parser generator in the general style of yacc. See http://www.haskell.org/happy for downloads and documentation.
happy uses a language description file to create a Haskell module that will do the parsing. Typical usage in in the second stage of a compiler, where it will be used to generate an abstract syntax tree.
1.2 Input File Structure
A happy file consists of four parts.
- The module header (Optional) : This is where you may define the module name and import other Haskell modules
- Various directives : This is used for definition of the tokens, the type of scanner to use, precedence setting.
- Grammar definition : The set of rules and actions
- The module trailer (Optional) : More Haskell code that can be used in the actions.