call_count/4¶

call_count(? CallsMax, ? RetriesMax, ? CallsAndRetriesMax)*

Set call counters as timers. YAP will generate an exception if one of the instantiated call counters decreases to 0:

• CallsMax

throw the exception call_counter when the counter calls reaches 0;

• RetriesMax

throw the exception retry_counter when the counter retries reaches 0;

• CallsAndRetriesMax

throw the exception call_and_retry_counter when the counter calls_and_retries reaches 0.

YAP will ignore counters that are called with unbound arguments.

Next, we show a simple example of how to use call counters:

 ?- prolog_flag(call_counting,on), [-user]. l :- l. end_of_file. current_prolog_flag(call_counting,off).

 yes

 yes
 ?- catch ((call_count(10000,_,_),l),call_counter,format( "limit_exceeded.~n" ,[])).

 limit_exceeded.

 yes

Notice that we first compile the looping predicate l//00with call_countingon. Next, we @ref catchU2fU_3 "catch//3"3 to handle an exception when @ref U60UlU2fU_0 "l//0"0performs more than 10000 reductions.