Possible Duplicate:Show that $\{xy \mid |x| = |y|, x\neq y\}$ is context-free Do there exist context-free grammars for the following two languages:The set of all strings of the form $xx$ where $x$ is a sequence of $0$'s and $1$'s. (For instance $0110101101$.)The set of all strings of the form $xy$ where $x$ and $y$ are sequences of $0$'s and $1$'s, $x$ and $y$ have the same length and $x\neq y$.
Are these two languages context free?
formal languages;context free