include "demo/natural_deduction_support.ma".
-lemma ex1 : ΠA,B,C,E: CProp.
+lemma RAA_to_EM : A ∨ ¬ A.
- (A ⇒ E) ∨ B ⇒ A ∧ C ⇒ (E ∧ C) ∨ B.
+ apply (prove (A ∨ ¬ A));
+
+ apply (RAA [H] ⊥);
+ apply (¬_e (¬A) A);
+ [ apply (¬_i [H1] ⊥);
+ apply (¬_e (¬(A∨¬A)) (A∨¬A));
+ [ apply [H];
+ | apply (∨_i_l A);
+ apply [H1];
+ ]
+ | apply (RAA [H2] ⊥);
+ apply (¬_e (¬(A∨¬A)) (A∨¬A));
+ [ apply [H];
+ | apply (∨_i_r (¬A));
+ apply [H2];
+ ]
+ ]
+qed.
+
+lemma RA_to_EM1 : A ∨ ¬ A.
+
+ apply (prove (A ∨ ¬ A));
+
+ apply (RAA [H] ⊥);
+ apply (¬_e (¬¬A) (¬A));
+ [ apply (¬_i [H2] ⊥);
+ apply (¬_e (¬(A∨¬A)) (A∨¬A));
+ [ apply [H];
+ | apply (∨_i_r (¬A));
+ apply [H2];
+ ]
+ | apply (¬_i [H1] ⊥);
+ apply (¬_e (¬(A∨¬A)) (A∨¬A));
+ [ apply [H];
+ | apply (∨_i_l A);
+ apply [H1];
+ ]
+ ]
+qed.
- intros 4 (A B C E);apply (prove ((A⇒E)∨B⇒A∧C⇒E∧C∨B));
+lemma ex0 : (A ⇒ ⊥) ⇒ A ⇒ B ∧ ⊤.
- (*NICE: TRY THIS ERROR!
- apply (⇒_i [H] (A∧C⇒E∧E∧C∨B));
- apply (⇒_i [K] (E∧E∧C∨B));
- OR DO THE RIGHT THING *)
+ apply (prove ((A ⇒ ⊥) ⇒ A ⇒ B∧⊤));
+
+ apply (⇒_i [H] (A ⇒ B∧⊤));
+ apply (⇒_i [H1] (B∧⊤));
+ apply (∧_i B ⊤);
+ [ apply (⊥_e ⊥);
+ apply (⇒_e (A ⇒ ⊥) A);
+ [ apply [H];
+ | apply [H1];
+ ]
+ | apply (⊤_i);
+ ]
+qed.
+
+lemma ex1 : (A ⇒ E) ∨ B ⇒ A ∧ C ⇒ (E ∧ C) ∨ B.
+
+ apply (prove ((A⇒E)∨B⇒A∧C⇒E∧C∨B));
+
apply (⇒_i [H] (A∧C⇒E∧C∨B));
apply (⇒_i [K] (E∧C∨B));
apply (∨_e ((A⇒E)∨B) [C1] (E∧C∨B) [C2] (E∧C∨B));
]
qed.
+lemma dmg : ¬(A ∨ B) ⇒ ¬A ∧ ¬B.
+
+ apply (prove (¬(A ∨ B) ⇒ ¬A ∧ ¬B));
+ apply (⇒_i [H] (¬A ∧ ¬B));
+
+ apply (¬_e (¬A) A);
+
+
+
+
+(*
lemma ex2: ΠN:Type.ΠR:N→N→CProp.
(∀a:N.∀b:N.R a b ⇒ R b a) ⇒ ∀z:N.(∃x.R x z) ⇒ ∃y. R z y.
]
]
qed.
+*)
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