//
// Undoes the effect of expStoreExplanation
//
void Egraph::expRemoveExplanation( )
{
assert( exp_undo_stack.size( ) >= 2 );
Enode * x = exp_undo_stack.back( );
exp_undo_stack.pop_back( );
Enode * y = exp_undo_stack.back( );
exp_undo_stack.pop_back( );
assert( x );
assert( y );
assert( !x->isEnil( ) );
assert( !y->isEnil( ) );
// We observe that we don't need to undo the rerooting
// of the explanation trees, because it doesn't affect
// correctness. We just have to reroot y on itself
assert( x->getExpParent( ) == y || y->getExpParent( ) == x );
if ( x->getExpParent( ) == y )
{
x->setExpParent( NULL );
x->setExpReason( NULL );
}
else
{
y->setExpParent( NULL );
y->setExpReason( NULL );
}
}
//
// Subroutine of explainStoreExplanation
// Re-root the tree containing x, in such a way that
// the new root is x itself
//
void Egraph::expReRootOn ( Enode * x )
{
Enode * p = x;
Enode * parent = p->getExpParent( );
Enode * reason = p->getExpReason( );
x->setExpParent( NULL );
x->setExpReason( NULL );
while( parent != NULL )
{
// Save grandparent
Enode * grandparent = parent->getExpParent( );
// Save reason
Enode * saved_reason = reason;
reason = parent->getExpReason( );
// Reverse edge & reason
parent->setExpParent( p );
parent->setExpReason( saved_reason );
#ifdef PEDANTIC_DEBUG
assert( checkExpTree( parent ) );
#endif
// Move the two pointers
p = parent;
parent = grandparent;
}
}