atom.fp

{- `atom` is a primitive, which returns true (T), when
    givea any valid atom as an argument, otherwise will
    yield false (F). `atom` is bottom preserving.
    Eg. atom:⊥ = ⊥

  rules:

  atom:x = x is an atom -> T; x != ⊥ -> F; ⊥

-} 

atom:A