29244f32f6
This upstreams the solve_by_elim tactic from Std. It is a key tactic needed by library_search.
24 lines
579 B
Text
24 lines
579 B
Text
/-
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Copyright (c) 2017 Mario Carneiro. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Mario Carneiro, Yury G. Kudryashov
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-/
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prelude
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import Init.Core
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namespace Sum
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deriving instance DecidableEq for Sum
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deriving instance BEq for Sum
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/-- Check if a sum is `inl` and if so, retrieve its contents. -/
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def getLeft? : α ⊕ β → Option α
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| inl a => some a
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| inr _ => none
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/-- Check if a sum is `inr` and if so, retrieve its contents. -/
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def getRight? : α ⊕ β → Option β
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| inr b => some b
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| inl _ => none
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end Sum
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