Conceptually, not at all: you simply create a copy of whatever data structure you are keeping in memory to bind names to values. (Notice that you are probably a

Conceptually, not at all: you simply create a copy of whatever data structure you are keeping in memory to bind names to values. (Notice that you are probably already using something like this to correctly resolve scopes -- so it's not like it's more work, either). In practice, I guess it depends on how much you care about performance and how 'smart' the functional runtime is. But if you're not writing a toy interpreter, you probably also need bytecode compilation, etc.