conditional usepackage given documentclass [duplicate]

Possible Duplicate:
Which document class is being used?

How would I conditionally `usepackage{enumitem}` if the document class is memoir (but not beamer)?

Could I use the etoolbox primitives, or do I have to define something using renewcommand?

My setup is that I have two documents — `memoir` document, and a `beamer` document — both including the same latex document, which does most of the includes.