'''
BC1.py -- first of several incremental implementation of backward
chaining to illustrate incremental development in CS4100, Artificial
Intelligence.This first version works only with a KB of "facts",
meaning positive ground literals (with no variables). BC2 will introduce
variables and the possibility of having more than one return value.
We use a dictionary to store the KB and its keys are predicates symbols:
i.e., the goals we are trying to prove.
'''
from unify import *

KBdict = {}  #Here we will store the knowledge base

def acquireKB(KBfname):
    kbfile = open(KBname)
    for aline in kbfile.readlines():
        nextF = FOLexp(aline)
        # now add the exp to the dictionary with its key
        if KBdict.hasKey[nextF.op]:
            KBdict[nextF.op] = += [nextF]
        else:
            KBdict[nextF.op] = [nextF]

def FOLBCtest(Qfname):
    queryfile = open(Qfname)
    for aline in queryfile.readlines():
        nextQ = FOLexp(aline)
        print "Query = " , nextQ
        #now find everything the query matches in the KB
        entries = KBdict[nextQ.op]
        for e in entries:
            print "RESULT for " e "  is  " unify(nextQ, e)