Ultimately the answer is to use a language in which passing a function reference is as easy as writing a singleton that implements an interface and passing a re

Ultimately the answer is to use a language in which passing a function reference is as easy as writing a singleton that implements an interface and passing a reference to that. (Or easier—in any language with decent function-passing support, writing a function and referencing it is generally going to be easier because fewer things are happening.) OO makes sense if the different types of behavior map to object identities and inheritance trees, because it generates a chain of implicit if statements that capture this logic. If they don't—e.g., a hit changes behavior depending on whether the attacker is proficient in the weapon, rather than depending on the weapon class or attacker class itself—you're likely better off writing the if statements yourself.