Fail gracefully when Node Table is full

[SSoelvsten]

The Adiar BDD package will inherently always struggle to deal with small decision diagrams in comparison to the classical depth-first implementations. Hence, combining a depth-first implementation with Adiar would create something that is the best of both worlds.

How I imagine this could be achieved is as follows:

• If Sylvan runs out of memory: Run Adiar's algorithms on the BDDs from Sylvan (wrapping the node table into something that works with Adiar's algorithms)
• If the output from Adiar is very small: During the Reduction Phase, create the nodes in Sylvan's unique node table instead in one of Adiar's files.

For this to work, I'd need Sylvan to not exit the entire program, if it runs out of memory. Instead, it needs to fail gracefully and merely returns a null pointer. Would that be a lot of work?