Exercises on reductions of CFG

  1. {g1,g2CFG({a,b})2L(g1)L(g2)}{G1,G2,G3L(G1)L(G2)    L(G1)L(G3)    L(G2)L(G3)}\{\langle g_1,g_2\rangle\in\mathtt{CFG}(\{a,b\})^2\mid\mathcal{L}(g_1)\cap\mathcal{L}(g_2)\neq\emptyset\}\quad\leq\quad\{\langle G_1,G_2,G_3\rangle\mid\mathcal{L}(G_1)\cap\mathcal{L}(G_2)\neq\emptyset\;\wedge\;\mathcal{L}(G_1)\cap\mathcal{L}(G_3)\neq\emptyset\;\wedge\;\mathcal{L}(G_2)\cap\mathcal{L}(G_3)\neq\emptyset\}
  2. {g1,g2CFG({a,b})2L(g1)L(g2)}{G1,G2,G3L(G1)L(G2)    L(G2)L(G3)    L(G1)L(G3)=}\{\langle g_1,g_2\rangle\in\mathtt{CFG}(\{a,b\})^2\mid\mathcal{L}(g_1)\cap\mathcal{L}(g_2)\neq\emptyset\}\quad\leq\quad\{\langle G_1,G_2,G_3\rangle\mid\mathcal{L}(G_1)\cap\mathcal{L}(G_2)\neq\emptyset\;\wedge\;\mathcal{L}(G_2)\cap\mathcal{L}(G_3)\neq\emptyset\;\wedge\;\mathcal{L}(G_1)\cap\mathcal{L}(G_3)=\emptyset\}
  3. {g1,g2CFG({a,b})2L(g1)L(g2)}{G1,G2,G3CFG({a,b})3L(G1)L(G2)    L(G2)L(G3)    L(G1)L(G3)=}\{\langle g_1,g_2\rangle\in\mathtt{CFG}(\{a,b\})^2\mid\mathcal{L}(g_1)\cap\mathcal{L}(g_2)\neq\emptyset\}\quad\leq\quad\{\langle G_1,G_2,G_3\rangle\in\mathtt{CFG}(\{a,b\})^3\mid\mathcal{L}(G_1)\cap\mathcal{L}(G_2)\neq\emptyset\;\wedge\;\mathcal{L}(G_2)\cap\mathcal{L}(G_3)\neq\emptyset\;\wedge\;\mathcal{L}(G_1)\cap\mathcal{L}(G_3)=\emptyset\}
  4. {g1,g2CFG({a,b})2L(g1)L(g2)}{G1,G2,G3,G4L(G1)L(G2)    L(G3)L(G4)    L(G1)L(G4)=    L(G2)L(G3)=}\{\langle g_1,g_2\rangle\in\mathtt{CFG}(\{a,b\})^2\mid\mathcal{L}(g_1)\cap\mathcal{L}(g_2)\neq\emptyset\}\quad\leq\quad\{\langle G_1,G_2,G_3,G_4\rangle\mid\mathcal{L}(G_1)\cap\mathcal{L}(G_2)\neq\emptyset\;\wedge\;\mathcal{L}(G_3)\cap\mathcal{L}(G_4)\neq\emptyset\;\wedge\;\mathcal{L}(G_1)\cap\mathcal{L}(G_4)=\emptyset\;\wedge\;\mathcal{L}(G_2)\cap\mathcal{L}(G_3)=\emptyset\}
  5. {g1,g2CFG({a,b})2L(g1)L(g2)}{G1,G2,G3,G4CFG({a,b})4L(G1)L(G2)    L(G3)L(G4)    L(G1)L(G4)=    L(G2)L(G3)=}\{\langle g_1,g_2\rangle\in\mathtt{CFG}(\{a,b\})^2\mid\mathcal{L}(g_1)\cap\mathcal{L}(g_2)\neq\emptyset\}\quad\leq\quad\{\langle G_1,G_2,G_3,G_4\rangle\in\mathtt{CFG}(\{a,b\})^4\mid\mathcal{L}(G_1)\cap\mathcal{L}(G_2)\neq\emptyset\;\wedge\;\mathcal{L}(G_3)\cap\mathcal{L}(G_4)\neq\emptyset\;\wedge\;\mathcal{L}(G_1)\cap\mathcal{L}(G_4)=\emptyset\;\wedge\;\mathcal{L}(G_2)\cap\mathcal{L}(G_3)=\emptyset\}
  6. {g1,g2CFG({a,b})2L(g1)L(g2)}{G1,G2L(G1)L(G2)2}\{\langle g_1,g_2\rangle\in\mathtt{CFG}(\{a,b\})^2\mid\mathcal{L}(g_1)\cap\mathcal{L}(g_2)\neq\emptyset\}\quad\leq\quad\{\langle G_1,G_2\rangle\mid|\mathcal{L}(G_1)\cap\mathcal{L}(G_2)|\geq 2\}
  7. {g1,g2CFG({a,b})2L(g1)L(g2)}{G1,G2CFG({a,b})2L(G1)L(G2)2}\{\langle g_1,g_2\rangle\in\mathtt{CFG}(\{a,b\})^2\mid\mathcal{L}(g_1)\cap\mathcal{L}(g_2)\neq\emptyset\}\quad\leq\quad\{\langle G_1,G_2\rangle\in\mathtt{CFG}(\{a,b\})^2\mid|\mathcal{L}(G_1)\cap\mathcal{L}(G_2)|\geq 2\}
  8. {gCFG({a,b})L(g)={a,b}}{GL(G)={a,b,c}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{a,b,c\}^*\}
  9. {gCFG({a,b})L(g)={a,b}}{G1,G2L(G1)=L(G2)}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{\langle G_1,G_2\rangle\mid\mathcal{L}(G_1)=\mathcal{L}(G_2)\}
  10. {gCFG({a,b})L(g)={a,b}}{G1,G2L(G1)L(G2)}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{\langle G_1,G_2\rangle\mid\mathcal{L}(G_1)\subseteq\mathcal{L}(G_2)\}
  11. {g1,g2CFG({a,b})2L(g1)L(g2)=}{G1,G2L(G1)L(G2)}\{\langle g_1,g_2\rangle\in\mathtt{CFG}(\{a,b\})^2\mid\mathcal{L}(g_1)\cap\mathcal{L}(g_2)=\emptyset\}\quad\leq\quad\{\langle G_1,G_2\rangle\mid\mathcal{L}(G_1)\subseteq\overline{\mathcal{L}(G_2)}\}
  12. {gCFG({a,b})L(g)={a,b}}{G1,G2L(G1)L(G2)}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{\langle G_1,G_2\rangle\mid\overline{\mathcal{L}(G_1)}\subseteq\mathcal{L}(G_2)\}
  13. {gCFG({a,b})L(g)={a,b}}{G1,G2L(G1)L(G2)}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{\langle G_1,G_2\rangle\mid\overline{\mathcal{L}(G_1)}\subseteq\overline{\mathcal{L}(G_2)}\}
  14. {gCFG({a,b})L(g)={a,b}}{GL(G)={wa:w{a,b}}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{wa : w\in\{a,b\}^*\}\}
  15. {gCFG({a,b})L(g)={a,b}}{GL(G)={waa:w{a,b}}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{waa : w\in\{a,b\}^*\}\}
  16. {gCFG({a,b})L(g)={a,b}}{GL(G)={a,b}{λ}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{a,b\}^*-\{\lambda\}\}
  17. {gCFG({a,b})L(g)={a,b}}{GL(G)={a,b}{a}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{a,b\}^*-\{a\}\}
  18. {gCFG({a,b})L(g)={a,b}}{GL(G)={a,b}{ab}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{a,b\}^*-\{ab\}\}
  19. {gCFG({a,b})L(g)={a,b}}{GL(G)={w{a,b}:wa1}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{w\in\{a,b\}^* : |w|_a\geq 1\}\}
  20. {gCFG({a,b})L(g)={a,b}}{GL(G)={w{a,b}:waa1}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{w\in\{a,b\}^* : |w|_{aa}\geq 1\}\}
  21. {gCFG({a,b})L(g)={a,b}}{GL(G)={w{a,b}:wa=wb}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{w\in\{a,b\}^* : |w|_a=|w|_b\}\}
  22. {gCFG({a,b})L(g)={a,b}}{GL(G)={w{a,b}:wawb}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{w\in\{a,b\}^* : |w|_a\neq|w|_b\}\}
  23. {gCFG({a,b})L(g)={a,b}}{GL(G)={w{0,1}kN:value2(w)=3k}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{w\in\{0,1\}^* \mid \exists k\in\mathbb{N}: \mathtt{value}_2(w)=3\cdot k\}\}
  24. {gCFG({a,b})L(g)={a,b}}{GL(G)={w{0,1}kN:value2(w)=3k+1}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{w\in\{0,1\}^* \mid \exists k\in\mathbb{N}: \mathtt{value}_2(w)=3\cdot k+1\}\}
  25. {gCFG({a,b})L(g)={a,b}}{GL(G)={w{0,1}kN:value2(w)=3k+2}}\{g\in\mathtt{CFG}(\{a,b\})\mid\mathcal{L}(g)=\{a,b\}^*\}\quad\leq\quad\{G\mid\mathcal{L}(G)=\{w\in\{0,1\}^* \mid \exists k\in\mathbb{N}: \mathtt{value}_2(w)=3\cdot k+2\}\}