timeout.yap

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/*************************************************************************
*                                    *
*    YAP Prolog                              *
*                                    *
*   Yap Prolog was developed at NCCUP - Universidade do Porto    *
*                                    *
* Copyright L.Damas, V.S.Costa and Universidade do Porto 1985-1997   *
*                                    *
**************************************************************************
*                                    *
* File:     timeout.yap                      *
* Last rev: 5/12/99                          *
* mods:                                  *
* comments: Goal within timeout                  *
*                                    *
*************************************************************************/
 
/**
 * @file   timeout.yap
 * @author VITOR SANTOS COSTA <vsc@VITORs-MBP.lan>
 * @date   Wed Nov 18 01:26:14 2015
 * 
 * @brief  Calls With Timeout
 * 
 * 
*/
 
 
:- module(timeout, [
    time_out/3
    ]).
 
 
/** @defgroup timeout Calls With Timeout
@ingroup YAPLibrary
@{
 
The <tt>time_out/3</tt> command relies on the <tt>alarm/3</tt> built-in to
implement a call with a maximum time of execution. The command is
available with the `use_module(library(timeout))` command.
 
  */
 
/*
  
 @pred time_out(+ _Goal_, + _Timeout_, - _Result_) 
 
 
Execute goal  _Goal_ with time limited  _Timeout_, where
 _Timeout_ is measured in milliseconds. If the goal succeeds, unify
 _Result_ with success. If the timer expires before the goal
terminates, unify  _Result_ with <tt>time_out</tt>.
 
This command is implemented by activating an alarm at procedure
entry. If the timer expires before the goal completes, the alarm will
throw an exception  _timeout_.
 
One should note that time_out/3 is not reentrant, that is, a goal
called from `time_out` should never itself call
time_out/3. Moreover, time_out/3 will deactivate any previous
alarms set by alarm/3 and vice-versa, hence only one of these
calls should be used in a program.
 
Last, even though the timer is set in milliseconds, the current
implementation relies on <tt>alarm/3</tt>, and therefore can only offer
precision on the scale of seconds.
 
 */
 
 
:- meta_predicate time_out(0,+,-).
 
:- virtual_alarm/3alarm/3use_module(library(hacks), [
    ,
    
    ]).
 
%
% not the nicest program I've ever seen.
%
 
 
time_out(Goal, Time, Result) :-
    T is (Time div 1000),
    UT is (Time*1000) mod 1000000,
       gated_call(
       alarm( T, UT, __OldT, _),
       Goal,
       Port,
       exit_time_out(Port, Goal, Result)),
       gated_call.
 
 
exit_time_out(_,_,_) :-
    alarm(0,0,_,_),
    alarm.
exit_time_out(Port, _, Result):-
       time_out_rc(Port, Result).
 
time_out_rc(exit, success).
time_out_rc(answer, success).
time_out_rc(fail, failure).
time_out_rc(exception(_), failure).
time_out_rc(external_exception(_), failure).
time_out_rc(redo, failure).
time_out_rc(!, success).
 
    clean_goal((A,B),(CA,CB)) :-
        clean_goal,
        clean_goal(A,CA),
        clean_goal(B,CB).
    clean_goal((A;B),(CA;CB)) :-
        clean_goal,
        clean_goal(A,CA),
        clean_goal(B,CB).
    clean_goal((A->B),(CA->CB)) :-
        clean_goal,
        clean_goal(A,CA),
        clean_goal(B,CB).
    clean_goal((A *->B),(CA *->CB)) :-
        clean_goal,
        clean_goal(A,CA),
        clean_goal(B,CB).
    clean_goal(user:A,CA) :-
        clean_goal,
        clean_goal(A,CA).
   clean_goal(prolog:A,CA) :-
        clean_goal,
        clean_goal(A,CA).
    clean_goal(A,A).
 
%% @}