SWI-Prolog -- call

Documentation
- Reference manual
  - Built-in Predicates
    - DCG Grammar rules
- Packages

Availability:built-in

call_dcg(:DCGBody, ?State0, ?State)

As phrase/3, but without type checking State0 and State. This allows for using DCG rules for threading an arbitrary state variable. This predicate was introduced after type checking was added to phrase/3.^{82After
discussion with Samer Abdallah.}

A portable solution for threading state through a DCG can be implemented by wrapping the state in a list and use the DCG semicontext facility. Subsequently, the following predicates may be used to access and modify the state:^{83This
solution was proposed by Markus Triska.}

state(S), [S] --> [S].
state(S0, S), [S] --> [S0].