SWI-Prolog -- API-function PL_query

Documentation
- Reference manual
  - Foreign Language Interface
    - The Foreign Include File
      - Calling Prolog from C
        
        Initiating a query from C
        
        PL_open_query()
        
        PL_next_solution()
        
        PL_cut_query()
        
        PL_close_query()
        
        PL_current_query()
        
        PL_query_engine()
        
        PL_query_arguments()
        
        PL_set_query_data()
        
        PL_query_data()
        
        PL_call_predicate()
        
        PL_call()
- Packages

Availability:C-language interface function

PL_engine_t PL_query_engine(qid_t qid)

Return the engine to which qid belongs. Note that interacting with a query or the Prolog terms associated with a query requires the engine to be current. See PL_set_engine().