Question

I’m writing an implementation of a virtual machine in C#, and I need to implement the VM’s stack, which can contain two types of entry – return entries or backtrack entries. What is the best way of implementing this?

I’m currently using a base type, as follows:

class StackEntry { } class Return : StackEntry { uint pc; } class Backtrack : StackEntry { uint pc; object backtrack; }  Stack<StackEntry> stack; 

This works OK, but the resulting type testing and downcasting feels clumsy.

Is there a better way of handling this type of construction?

Answer 1

I’m having a hard time imagining how you’re going to use this, but the basic answer is that you use a single type with a default operation for post-pop processing

StackEntry { protected virtual void PostPop(); } Return : StackEntry { protected override void PostPop(); } Backtrack : StackEntry { protected override void PostPop(); } 

Does that make sense?