30 lines
865 B
Text
30 lines
865 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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Authors: Leonardo de Moura
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-/
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prelude
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import init.data.fin.basic
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open nat
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def unsigned_sz : nat := succ 4294967295
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def unsigned := fin unsigned_sz
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namespace unsigned
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/- We cannot use tactic dec_trivial here because the tactic framework has not been defined yet. -/
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private lemma zero_lt_unsigned_sz : 0 < unsigned_sz :=
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zero_lt_succ _
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/- Later, we define of_nat using mod, the following version is used to define the metaprogramming system. -/
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protected def of_nat' (n : nat) : unsigned :=
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if h : n < unsigned_sz then fin.mk n h else fin.mk 0 zero_lt_unsigned_sz
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def to_nat (c : unsigned) : nat :=
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fin.val c
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end unsigned
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instance : decidable_eq unsigned :=
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have decidable_eq (fin unsigned_sz), from fin.decidable_eq _,
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this
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