34 lines
963 B
Text
34 lines
963 B
Text
/-
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Copyright (c) 2016 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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-/
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prelude
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import init.nat
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open nat
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structure fin (n : nat) := (val : nat) (is_lt : val < n)
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namespace fin
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attribute fin.val [coercion]
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variable {n : nat}
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lemma eq_of_veq : ∀ {i j : fin n}, (val i) = j → i = j
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| (mk iv ilt) (mk jv jlt) := assume (veq : iv = jv), sorry -- begin congruence, assumption end
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lemma veq_of_eq : ∀ {i j : fin n}, i = j → (val i) = j
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| (mk iv ilt) (mk jv jlt) := assume Peq,
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show iv = jv, from fin.no_confusion Peq (λ Pe Pqe, Pe)
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lemma eq_iff_veq {i j : fin n} : (val i) = j ↔ i = j :=
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iff.intro eq_of_veq veq_of_eq
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end fin
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open decidable fin
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protected definition fin.has_decidable_eq [instance] (n : nat) : ∀ (i j : fin n), decidable (i = j)
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| (mk ival ilt) (mk jval jlt) :=
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decidable_of_decidable_of_iff (nat.has_decidable_eq ival jval) eq_iff_veq
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