built-in predicate

# `threaded/1`

## Description

    threaded(Goals)

    threaded(Conjunction)
    threaded(Disjunction)

Proves each goal in a conjunction (disjunction) of goals in its own thread. This predicate is deterministic and opaque to cuts. The predicate argument is not flattened.

When the argument is a conjunction of goals, a call to this predicate blocks until either all goals succeed, one of the goals fail, or one of the goals generate an exception; the failure of one of the goals or an exception on the execution of one of the goals results in the termination of the remaining threads. The predicate call is true iff all goals are true.

When the argument is a disjunction of goals, a call to this predicate blocks until either one of the goals succeeds, all the goals fail, or one of the goals generate an exception; the success of one of the goals or an exception on the execution of one of the goals results in the termination of the remaining threads. The predicate call is true iff one of the goals is true.

When the predicate argument is neither a conjunction not a disjunction of goals, no threads are used. In this case, the predicate call is equivalent to a `once/1` predicate call.

Note

This predicate requires a backend Prolog compiler providing compatible multi-threading primitives. The value of the read-only threads flag is set to `supported` when that is the case.

## Modes and number of proofs

    threaded(+callable) - zero_or_one

## Errors

`Goals` is a variable:
`instantiation_error`
A goal in `Goals` is a variable:
`instantiation_error`
`Goals` is neither a variable nor a callable term:
`type_error(callable, Goals)`
A goal `Goal` in `Goals` is neither a variable nor a callable term:
`type_error(callable, Goal)`

## Examples

Prove a conjunction of goals, each one in its own thread:
`threaded((Goal, Goals))`
Prove a disjunction of goals, each one in its own thread:
`threaded((Goal; Goals))`

See also

threaded_call/1-2, threaded_once/1-2, threaded_ignore/1, synchronized/1