// Constraints up to but not including iterator it have been unified.
// The current solution is soln
// The set of all solutions is in solns
bool Constraints::doSolve(std::list<Exp*>::iterator it, ConstraintMap& soln, std::list<ConstraintMap>& solns) {
LOG << "Begin doSolve at level " << ++level << "\n";
LOG << "Soln now: " << soln.prints() << "\n";
if (it == disjunctions.end()) {
// We have gotten to the end with no unification failures
// Copy the current set of constraints as a solution
//if (soln.size() == 0)
// Awkward. There is a trivial solution, but we have no constraints
// So make a constraint of always-true
//soln.insert(new Terminal(opTrue));
// Copy the fixed constraints
soln.makeUnion(fixed);
solns.push_back(soln);
LOG << "Exiting doSolve at level " << level-- << " returning true\n";
return true;
}
Exp* dj = *it;
// Iterate through each disjunction d of dj
Exp* rem1 = dj; // Remainder
bool anyUnified = false;
Exp* d;
while ((d = nextDisjunct(rem1)) != NULL) {
LOG << " $$ d is " << d << ", rem1 is " << ((rem1==0)?"NULL":rem1->prints()) << " $$\n";
// Match disjunct d against the fixed types; it could be compatible,
// compatible and generate an additional constraint, or be
// incompatible
ConstraintMap extra; // Just for this disjunct
Exp* c;
Exp* rem2 = d;
bool unified = true;
while ((c = nextConjunct(rem2)) != NULL) {
LOG << " $$ c is " << c << ", rem2 is " << ((rem2==0)?"NULL":rem2->prints()) << " $$\n";
if (c->isFalse()) {
unified = false;
break;
}
assert(c->isEquality());
Exp* lhs = ((Binary*)c)->getSubExp1();
Exp* rhs = ((Binary*)c)->getSubExp2();
extra.insert(lhs, rhs);
ConstraintMap::iterator kk;
kk = fixed.find(lhs);
if (kk != fixed.end()) {
unified &= unify(rhs, kk->second, extra);
LOG << "Unified now " << unified << "; extra now " << extra.prints() << "\n";
if (!unified) break;
}
}
if (unified)
// True if any disjuncts had all the conjuncts satisfied
anyUnified = true;
if (!unified) continue;
// Use this disjunct
// We can't just difference out extra if this fails; it may remove
// elements from soln that should not be removed
// So need a copy of the old set in oldSoln
ConstraintMap oldSoln = soln;
soln.makeUnion(extra);
doSolve(++it, soln, solns);
// Revert to the previous soln (whether doSolve returned true or not)
// If this recursion did any good, it will have gotten to the end and
// added the resultant soln to solns
soln = oldSoln;
LOG << "After doSolve returned: soln back to: " << soln.prints() << "\n";
// Back to the current disjunction
it--;
// Continue for more disjuncts this disjunction
}
// We have run out of disjuncts. Return true if any disjuncts had no
// unification failures
LOG << "Exiting doSolve at level " << level-- << " returning " << anyUnified << "\n";
return anyUnified;
}
