Published online by Cambridge University Press: 15 April 2002
We investigate the complexity of languages described by some expressionscontaining shuffle operator and intersection. We show that deciding whetherthe shuffle of two words has a nonempty intersection with a regular set(or fulfills some regular pattern) is NL-complete.Furthermore we show that the class of languages of the form $L\cap R$ ,with a shuffle language L and a regular language R, containsnon-semilinear languages and does not form a family of mildlycontext-sensitive languages.