The type nfa_t is the type representing NFAs. It is modeled after the formal definition of an NFA, a 5-tuple (Q, Σ, δ, q0, F) where: Q is a finite set of states, Σ is a finite alphabet, δ : Q × (Σ ∪ ...
In a call to string_to_regexp s the string s may contain only parentheses, |, *, a-z (lowercase), and E (for epsilon). A grammatically ill-formed string will result in IllegalExpression being thrown.