18 lines
444 B
Text
18 lines
444 B
Text
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import data.nat
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open nat
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structure less_than (n : nat) := (val : nat) (lt : val < n)
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namespace less_than
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open decidable
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set_option pp.beta false
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definition less_than.has_decidable_eq [instance] (n : nat) : ∀ (i j : less_than n), decidable (i = j)
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| (mk ival ilt) (mk jval jlt) :=
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match nat.has_decidable_eq ival jval with
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| inl veq := inl (by substvars)
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| inr vne := inr (by intro h; injection h; contradiction)
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end
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end less_than
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