[dmurray]

> I don't expect that I can download a library that does A* on abstract state spaces not fully present in RAM for me

I'm sure this does exist! A functional library where you pass in, not a pointer to the set of all nodes, but some functions to get the node with the current lowest distance and to update the distance of a node.

Not saying it was the right thing for your use case, but don't rule it out. Even in languages that aren't strongly FP - eg it happens a lot in Go due to the lack of generics, and if you squint, the C++ STL is kind of like this.