Definitely possible. Implementation will be different depending on what language you're using but if you're using C/C++ then it could be done through function pointers or polymorphism.

Function pointers: Have several functions, one for each type of AI and have them all use the same footprint (e.g. return the same type, accept the same number and types of parameters in the same order). Then use a function pointer for each AI object and make it point to the required function.

Polymorphism: Have an interface class to be the base for AI classes and then implement several classes, one for each type of AI. Then give each AI object a pointer to the base class and simply assign it to point at an object of the desired AI type.

Tactically speaking, you have other solutions that might give you good results, however they require much more work from you - Genetic Algorithms that you can use to train your population of enemies, and Full State Machines to determine different types of behaviours. The previous is harder but ensures a *smarter* AI, and the latter is the one I recommend to begin with. Search the articles for resources on both techniques.

Son Of Cain

In my previous post, rather than *smarter*, a Genetic Algorithm can help you achieve a more *natural* AI. In other words, you can specify several types of behaviours for different situations by training the entity's characteristics against them.