DSL extensions #

You can define your own DSL clauses; the built-in ones are themselves defined through this mechanism.

This is most useful if you want to define a custom filter rule, or group a frequently used sequence of clauses under a meanigful name.

The basic form for an extension is:

dsl {
  section [ :forall | :make ]
  clause :my_action

  # one of the following:

  body {
    # ...
  }

  action class
  action { |token|
    # ...
  }

  accept class

}

body needs to contain other matchers or actions; it is essentially an alias for a commonly reused group.

action works the same way as the built-in action clause, but gives it a meaningful name, which may improve readability.

For example, this is how you can define custom collectors:

dsl {
  section :make
  clause :my_collection
  action Wongi::Engine::SimpleCollector.collector
}

rule {
  # ...
  make {
    my_collection :X
  }
}

collection = engine.collection :my_collection

accept defines an intermediate state in rule compilation; the class needs to define #import_into(engine), which needs to return an object conforming to the action interface.