The method Prolog.query()
returns an instance of the JavaScript class Query that may
be used to explore the solutions of the query. The Query
class implements the JavaScript iterator protocol.
- Object Query.next()
- Implements the iterator protocol. This returns an object
holding the keys
done and value. If exception
handling is enabled it returns an object
{done:true, error:true,
message:String}.
- Object Query.once()
- Close the query after the first answer. Returns the
.value
of the object returned by .next() on success and the
complete object on failure or error. In addition, on a logical result
(no error), a field
success is added with a boolean value. Thus, the return
value may contain these keys:
- {Bindings}
- Query succeeded. Objects holds a key for each output variable. In
addition the
success key is set to true.
- {
success:false} - Query failed. Note that the binding keys all start with an uppercase
letter and this is thus not ambiguous.
- {
error:true, message:String} - Query raised an exception.
- Object Query.close()
- Closes the query. This can be used inside the iterator to stop further
enumeration.
