If I make a function called allocate_new_foo() that is not an abstraction (in the sense I mentioned - i.e. method dispatching). It's plain old boring programmin

If I make a function called allocate_new_foo() that is not an abstraction (in the sense I mentioned - i.e. method dispatching). It's plain old boring programming - specifying in only one place how foo's should be allocated. And each caller is expected to have a good understanding what kind of allocation to expect - i.e. pool allocation or whatever. I wouldn't consider this an abstraction at all, and it doesn't leak nearly as much as a "streams" abstraction - if at all.