37 lines
625 B
Text
37 lines
625 B
Text
import data.nat
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open tactic nat
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example (a b : nat) : a ≠ b → ¬ a = b :=
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by do
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intros,
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by_contradiction `H,
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trace_state,
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contradiction
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print "-------"
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example (a b : nat) : ¬¬ a = b → a = b :=
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by do
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intros,
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by_contradiction `H,
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trace_state,
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contradiction
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print "-------"
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example (p q : Prop) : ¬¬ p → p :=
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by do
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intros,
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by_contradiction `H, -- should fail
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trace_state
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print "-------"
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local attribute classical.prop_decidable [instance] -- Now all propositions are decidable
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example (p q : Prop) : ¬¬p → p :=
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by do
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intros,
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by_contradiction `H,
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trace_state,
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contradiction
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