1 votes 1 votes Use Ogden's lemma $($Question $2)$ to simplify the proof in example $7.21$ that $L=\{\text{ww|w is in $\{0,1\}^{*}$}\}$ is not a $CFL.$Hint$:$With $z=0^{n}1^{n}0^{n}1^{n},$ make the two middle blocks distinguished. Theory of Computation ullman theory-of-computation context-free-language + – admin asked Apr 11, 2019 • edited Apr 11, 2019 by Lakshman Bhaiya admin 109 views answer comment Share Follow See all 0 reply Please log in or register to add a comment.