Phrase Structure Grammars
Closure and Decidability Properties

Property0123
Reversal ++++
Concatenation ++++
Intersection with Regular Sets ++++
Union ++++
Intersection -+-+
Complement -+-+
Concatenation ++++
L(G) Empty? --++
L(G) Finite? --++
L(G) Infinite? --++
L1 ≡ L2? ---+
L1 ⊆ L2? ---+
L(G) = Σ*? ---+
S ⇒ x for some x? -+++
S ⇒ w x y for some x? --++
Ambiguous? ---+
Arbitrary language of this type? ----
∃ an equivalent unambiguous grammar? + -+
λ in L(G)? +++
L(G) = {λ}? ++