Some of the predicates below are designed to operate in a DCG where the state represents a time as a number of seconds since a particular epoch (see get_time/1). The enables the write of code in a sort of temporal modal logic form, where predicates can implicitly get at the current time (using get//1) or move to other times by chaging the DCG state.

 now(-T:time)// is det

Unifies T with the current real time as returned by get_time/1.

 wait// is semidet

 wait(+Pre:nonneg)// is semidet

Waits (blocks) until the real world time catches up with the current DCG time. If Pre is given, then wait//1 sleeps until Pre seconds before the current DCG time.

 sleep_till(+T:time) is semidet

Compares T with the current real time (get_time/1); if T is in the past, then fail, otherwise, blocks until approximately T. Accuracy of timing cannot be guaranteed.

 sync// is det

Runs in time DCG and sets the current time to the current real time as returned by now//1 and get_time/1.

 adv(+T:nonneg)// is det

Advances current time by T seconds. Runs in time DCG.

 cue(+D:nonneg)// is det

Sets the current DCG time to D seconds after current real time.

 cue(+D:nonneg, +Q:nonneg)// is det

Sets the current DCG time to next multiple of Q at least D seconds after current real time.

 run_cued(+DT:nonneg, +Q:nonneg, +Cmd:phrase((time,S)), ?S1:S, ?S2:S) is nondet

 run_cued(+DT:nonneg, +Cmd:phrase((time,S)), ?S1:S, ?S2:S) is nondet

 run_cued(+DT:nonneg, +Q:nonneg, +Cmd:phrase(time)) is nondet

 run_cued(+DT:nonneg, +Cmd:phrase(time)) is nondet

Run command Cmd in DT seconds. Cmd must operate in (time,S) DCG and is called with the current real time plus DT seconds. If Q is supplied, the time passed to Cmd is quantised upwards in units of Q seconds.

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 wait(Arg1, Arg2, Arg3)

 run_cued(Arg1, Arg2, Arg3, Arg4)

 run_cued(Arg1, Arg2)

 run_cued(Arg1, Arg2, Arg3)