Exercises on reductions of CFG

  1. {⟨g1,g2⟩∈CFG({a,b})2∣L(g1)∩L(g2)≠∅}≤{⟨G1,G2,G3⟩∣L(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,g2⟩∈CFG({a,b})2∣L(g1)∩L(g2)≠∅}≤{⟨G1,G2,G3⟩∣L(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,g2⟩∈CFG({a,b})2∣L(g1)∩L(g2)≠∅}≤{⟨G1,G2,G3⟩∈CFG({a,b})3∣L(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,g2⟩∈CFG({a,b})2∣L(g1)∩L(g2)≠∅}≤{⟨G1,G2,G3,G4⟩∣L(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,g2⟩∈CFG({a,b})2∣L(g1)∩L(g2)≠∅}≤{⟨G1,G2,G3,G4⟩∈CFG({a,b})4∣L(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,g2⟩∈CFG({a,b})2∣L(g1)∩L(g2)≠∅}≤{⟨G1,G2⟩∣∣L(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,g2⟩∈CFG({a,b})2∣L(g1)∩L(g2)≠∅}≤{⟨G1,G2⟩∈CFG({a,b})2∣∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{⟨G1,G2⟩∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{⟨G1,G2⟩∣L(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,g2⟩∈CFG({a,b})2∣L(g1)∩L(g2)=∅}≤{⟨G1,G2⟩∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{⟨G1,G2⟩∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{⟨G1,G2⟩∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(G)={w∈{a,b}∗:∣w∣a≥1}}\{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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(G)={w∈{a,b}∗:∣w∣aa≥1}}\{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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(G)={w∈{a,b}∗:∣w∣a=∣w∣b}}\{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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(G)={w∈{a,b}∗:∣w∣a≠∣w∣b}}\{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. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(G)={w∈{0,1}∗∣value2(w)∈3N}}\{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 \mathtt{value}_2(w) \in 3\mathbb{N}\}\}
  24. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(G)={w∈{0,1}∗∣value2(w)∈3N+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 \mathtt{value}_2(w) \in 3\mathbb{N}+1\}\}
  25. {g∈CFG({a,b})∣L(g)={a,b}∗}≤{G∣L(G)={w∈{0,1}∗∣value2(w)∈3N+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 \mathtt{value}_2(w) \in 3\mathbb{N}+2\}\}