Calling Prolog from Java

A Prolog call is an instance of the class bprolog.plc.Plc. It is convenient to import the class first:

      import bprolog.plc.Plc;

The class Plc contains the following constructor and methods:

• public Plc(String functor, Object args[]): It constructs a prolog call where functor is the predicate name, and args is the sequence of arguments of the call. If a call does not carry any argument, then just give the second argument an empty array new Object[] .

• public static void startPlc(String args[]): Initialize the B-Prolog emulator, where args are parameter-value pairs given to B-Prolog. Possible parameter-value pairs include:

  "-b" TRAIL	words allocated to the trail stack
  "-s" STACK	words allocated to the local and the heap
  "-p" PAREA	words allocated to the program code area
  "-t" TABLE	words allocated to the table area

  where TRAIL, STACK, PAREA and TABLE must all be strings of integers. After the B-Prolog emulator is initialized, it will be waiting for calls from Java. Initialization needs to be done only once. Further calls to startPlc have no effect at all.

• public static native boolean exec(String command): Execute a Prolog call as represented by the string command. This method is static, and thus can be executed without creating any Plc object. To call a predicate in a file, say xxx.pl, it is necessary to first have the Prolog program loaded into the system. To do so, just execute the method exec("load(xxx)") or exec("consult(xxx)").

• public boolean call(): Execute the Prolog call as represented by the Plc object that owns this method. The return value is true if the Prolog call succeeds or false if the call fails.