ea6eee516b
Motivation: use same separator used in lambda expressions as in other programming languages.
59 lines
1.6 KiB
Text
59 lines
1.6 KiB
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.repr
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universes u v
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inductive Ordering
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| lt | Eq | gt
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instance : HasRepr Ordering :=
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⟨(fun s => match s with | Ordering.lt => "lt" | Ordering.Eq => "Eq" | Ordering.gt => "gt")⟩
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namespace Ordering
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def swap : Ordering → Ordering
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| lt := gt
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| Eq := Eq
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| gt := lt
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@[inline] def orElse : Ordering → Ordering → Ordering
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| lt _ := lt
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| Eq o := o
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| gt _ := gt
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theorem swapSwap : ∀ (o : Ordering), o.swap.swap = o
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| lt := rfl
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| Eq := rfl
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| gt := rfl
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end Ordering
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@[inline] def cmpUsing {α : Type u} (lt : α → α → Prop) [DecidableRel lt] (a b : α) : Ordering :=
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if lt a b then Ordering.lt
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else if lt b a then Ordering.gt
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else Ordering.Eq
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def cmp {α : Type u} [HasLess α] [DecidableRel (HasLess.Less : α → α → Prop)] (a b : α) : Ordering :=
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cmpUsing HasLess.Less a b
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instance : DecidableEq Ordering :=
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{decEq := fun a b =>
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match a with
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| Ordering.lt =>
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match b with
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| Ordering.lt => isTrue rfl
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| Ordering.Eq => isFalse (fun h => Ordering.noConfusion h)
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| Ordering.gt => isFalse (fun h => Ordering.noConfusion h)
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| Ordering.Eq =>
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match b with
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| Ordering.lt => isFalse (fun h => Ordering.noConfusion h)
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| Ordering.Eq => isTrue rfl
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| Ordering.gt => isFalse (fun h => Ordering.noConfusion h)
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| Ordering.gt =>
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match b with
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| Ordering.lt => isFalse (fun h => Ordering.noConfusion h)
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| Ordering.Eq => isFalse (fun h => Ordering.noConfusion h)
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| Ordering.gt => isTrue rfl}
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