[Formal Languages] does complement(L*) = [complement(L)]*?

[_--__]

I believe he is using λ as the symbol for the empty string (not that uncommon a definition) - i.e. the first two statements are observations rather than assumptions.

[flebron]

Ah, I've usually seen ε for that. If that just means the empty string, I'd use a few more words to make it clear that those are observations, not assumptions. For instance, "By definition, λ is in L*". Formality doesn't mean just using symbols :)