37 lines
1 KiB
Text
37 lines
1 KiB
Text
Variable N : Type
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Variable h : N -> N -> N
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(* Specialize congruence theorem for h-applications *)
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Theorem CongrH {a1 a2 b1 b2 : N} (H1 : a1 = b1) (H2 : a2 = b2) : (h a1 a2) = (h b1 b2) :=
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Congr (Congr (Refl h) H1) H2
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(* Declare some variables *)
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Variable a : N
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Variable b : N
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Variable c : N
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Variable d : N
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Variable e : N
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(* Add axioms stating facts about these variables *)
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Axiom H1 : (a = b ∧ b = c) ∨ (a = d ∧ d = c)
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Axiom H2 : b = e
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(* Proof that (h a b) = (h c e) *)
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Theorem T1 : (h a b) = (h c e) :=
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DisjCases H1
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(fun C1 : _,
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CongrH (Trans (Conjunct1 C1) (Conjunct2 C1)) H2)
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(fun C2 : _,
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CongrH (Trans (Conjunct1 C2) (Conjunct2 C2)) H2)
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(* We can use theorem T1 to prove other theorems *)
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Theorem T2 : (h a (h a b)) = (h a (h c e)) :=
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CongrH (Refl a) T1
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(* Display the last two objects (i.e., theorems) added to the environment *)
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Show Environment 2
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(* Show implicit arguments *)
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Set lean::pp::implicit true
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Set pp::width 150
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Show Environment 2
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