def join_empty_LHS(call,params,new_call2,new_params2,old_call2,old_params2,preds,empty2):
# RHS: call + params
# new top call: new_call2 + new_params2
#
# first we find a mapping of internal parameters from the predicate "call"
# to the internal parameters of the predicate "new_call2"
# * internal call parameter (preds[call][0]) -> top level params (params)
# -> new top level params (new_params2) -> internal new top call parameter (preds[new_call2][0])
# * internal parameter from the call equal to nil are translated into "nil-Xn" internal parameters of the new call
call_p_map={}
nil_pos=1
for i in range(len(preds[call][0])):
if params[i]=="nil":
call_p_map[preds[call][0][i]]="nil-X%i"%nil_pos
if not ("nil-X%i"%nil_pos in preds[new_call2][0]):
raise JoinFailed("JOIN: ERROR: this line should not be accesible")
nil_pos=nil_pos+1
elif params[i] in new_params2:
call_p_map[preds[call][0][i]]=preds[new_call2][0][new_params2.index(params[i])]
elif params[i] in old_params2:
# handle the param on which the join is applied if "to_remove was true" (-->this param is not part of new_params2)
call_p_map[preds[call][0][i]]=preds[old_call2][0][old_params2.index(params[i])]
else:
raise JoinFailed("JOIN: ERROR: this line should not be accesible")
# map the empty2 inside the rule.
if not len(empty2)==1:
raise JoinFailed("JOIN: not implemented")
# we suppose that the equality contains only a single disjunct
# the other situation is not implemented
disj=empty2[0]
equal=[]
for conj in disj:
new_conj=[]
for x in conj:
new_conj.append(preds[old_call2][0][old_params2.index(x)])
if x=="nil":
new_conj.append("nil")
equal.append(new_conj)
equal1=[]
for x in equal:
equal1.append(input.remove_multiple_occurences(x))
equal1=input.join_equalities(equal1)
new_rule_params=preds[new_call2][0]
# in the forbid variable, we store parameters, which are checked for the following:
# they must be existentially quantified
# they must be used only in call and call2
forbid=[]
# for each rule create a new rule
new_rules=[]
for (al,pt,cls,eq) in preds[call][1]:
# the system of predicates must be forward connected, so call_p_map[al] must be defined ...
alloc=call_p_map[al]
# find representatives
mapping={}
for conj in equal1:
if alloc in conj:
repres=alloc
else:
tmp=input.intersect_lists(new_rule_params,conj)
if tmp>1:
# equality between formal parameters implemented only if they are equal to the allocated node
if "nil" in conj:
for x in conj:
if x=="nil":
pass
else:
if new_params2[new_rule_params.index(x)]=="nil":
repres=x
else:
# add to the forbid
to_forbid=new_params2[new_rule_params.index(x)]
if not (to_forbid in forbid):
forbid.append(to_forbid)
else:
raise JoinFailed("JOIN: not implemented")
elif tmp==1:
for p in new_rule_params:
if p in conj:
repres=dp
else:
repres=conj[0]
for x in conj:
mapping[x]=repres
# the original rule is translated as folows:
# first all variables are translated according to the "all_p_map"
# every variable outside all_p_map is translated to an unique new name
# second all variables are translated according to the "mapping"
new_al=apply_maps(al,call_p_map,mapping,new_params2,0)
new_pt=[]
for x in pt:
new_pt.append(apply_maps(x,call_p_map,mapping,new_params2,0))
new_cls=[]
for (call_pred,call_par) in cls:
new_call_par=[]
for x in call_par:
new_call_par.append(apply_maps(x,call_p_map,mapping,new_params2,0))
new_cls.append((call_pred,new_call_par))
new_eq=[]
for x in eq:
new_eq.append(apply_maps(x,call_p_map,mapping,new_params2,1))
for x in mapping.keys():
if mapping[x]==new_al and (not x in new_eq):
new_eq.append(x)
# pop alocated node fron the equality list - not needed
if new_al in new_eq:
new_eq.pop(new_eq.index(new_al))
new_rules.append((new_al,new_pt,new_cls,new_eq))
# add the newly created rules inside preds
par,rules=preds[new_call2]
rules=rules+new_rules
preds[new_call2]=(par,rules)
return forbid
def join(preds,top_calls,emptyheap_eq,ex_quantified):
# it emptyheap_eq==[] then join sould not create some empty heap - assert in the furure
work_with_emptyheap=(not emptyheap_eq==[])
while len(top_calls)>1:
# pick the first call for the join
call,params=top_calls.pop(0)
if emptyheap_eq==[]:
empty=[]
else:
empty=emptyheap_eq.pop(0)
#find a second call for a join
# maximal number of attempts is given by the number of top calls
candidate=""
count=0
while (candidate=="") and (count<len(top_calls)):
count=count+1
find=0
for i in range(len(top_calls)):
call2,params2=top_calls[i]
if emptyheap_eq==[]:
empty2=[]
else:
empty2=emptyheap_eq[i]
p_intersect=create_intersection(params,params2)
if not (p_intersect==[] or (len(p_intersect)==1 and "nil" in p_intersect)):
top_calls.pop(i)
if not emptyheap_eq==[]:
emptyheap_eq.pop(i)
find=1
break
if find==0:
raise JoinFailed("Join failed")
# find the candidate variable
# - the candidate must be allocated in head of one of the calls
# - the candidate must be an existentially quantified variable
# - the candidate must be a link only between these two calls
candidate=""
for par in p_intersect:
if (input.alloc(call,params.index(par),preds)):
candidate=par
if candidate=="":
# swap positions of call and call2
call_aux=call
call=call2
call2=call_aux
params_aux=params
params=params2
params2=params_aux
empty_aux=empty
empty=empty2
empty2=empty_aux
for par in p_intersect:
if (input.alloc(call,params.index(par),preds)):
candidate=par
if candidate=="":
# still no success, push call (originally call2) back to topcalls
# swap back call2 to call
# then we will try so other item from topcall as call2
top_calls.append((call,params))
if work_with_emptyheap:
emptyheap_eq.append(empty)
(call,params,empty)=(call2,params2,empty2)
# check whether the candidate was found
if candidate=="":
raise JoinFailed("Join failed: impossible to join the input into a single predicate call (or bad strategy)")
if candidate=="nil":
raise JoinFailed("Something odd happened: nil taken as a candidate. nil existantially quantified in RootCall?")
# create a list of other parameters (different from candidate and nil) shared between the two calls
# pop the "candidate"
p_intersect.pop(p_intersect.index(candidate))
# pop all "nil" variables
while "nil" in p_intersect:
p_intersect.pop(p_intersect.index("nil"))
#the candidate is removed from the parameters after join
# if is it existentially quantified and it is not a parameter of other top level call
to_remove=candidate in ex_quantified
for (callX,paramsX) in top_calls:
if candidate in paramsX:
to_remove=False
#raise JoinFailed("Join failed: parameter %s is in more the two calls on top level"%candidate)
(call,params,empty,forbid)=do_join(candidate,call,params,empty,call2,params2,empty2,preds,p_intersect,to_remove)
# check that variables in forbid are no more part of top calls and forbid is ex_quantificated
for x in forbid:
if not x in ex_quantified:
raise JoinFailed("JOIN: forbiden variable is not existentially quantified")
for (c,p) in top_calls:
if input.intersect_lists(p,forbid)>0:
raise JoinFailed("JOIN: forbiden variable in other calls")
# add the newly created top call
top_calls.append((call,params))
if work_with_emptyheap:
emptyheap_eq.append(empty)
elif (not empty==[]):
raise JoinFailed("JOIN: ERROR: created emptyheap from some non-empty stuff")
root_rule,root_params=top_calls[0]
if emptyheap_eq==[]:
ret_empty=[]
else:
ret_empty=emptyheap_eq[0]
return (root_rule,root_params,ret_empty)