'Doing this globally at module init time is a pain ...'

def __init__(self):

    self.symbolic_formulae = {}
    self.concrete_formulae = {}
    self.formulae = []
    add_formulae(self.formulae)
    for f in self.formulae:
        sizes = f.func.sizes
        if (len(f.symbols) > 0):
            self.symbolic_formulae.setdefault(sizes, []).append(f)
        else:
            inv = f.func.build_invariants()
            self.concrete_formulae.setdefault(sizes, {})[inv] = f
