In my eyes an ideal library should not contain state, internally allocate (unless very obviously), or manage processes. The application should do that, or provide primitives for doing it which the library can make use of. That makes applications and libraries very very different in my mind.
The thing about state is a good point. With the sans-IO pattern we have inversion of IO and Time, but adding memory to that would be a nice improvement too.
Those C libraries that have initializers which take ** and do the allocation for you drive me nuts! I’m sure there’s some good reason, but can’t you trust me to allocate for myself, you know?
