41 lines
939 B
Text
41 lines
939 B
Text
/-
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Copyright (c) 2019 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: Daniel Selsam
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Simple stack API implemented using an array.
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-/
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prelude
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import Init.Data.Array
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import Init.Data.Int
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universes u v w
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structure Stack (α : Type u) :=
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(vals : Array α := Array.empty)
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namespace Stack
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variable {α : Type u}
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def empty : Stack α :=
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{ vals := Array.empty }
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def isEmpty (s : Stack α) : Bool :=
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s.vals.isEmpty
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def push (v : α) (s : Stack α) : Stack α :=
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{ vals := s.vals.push v .. s }
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def peek? (s : Stack α) : Option α :=
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if s.vals.isEmpty then none else s.vals.get? (s.vals.size-1)
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def peek! [Inhabited α] (s : Stack α) : α :=
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s.vals.back
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def pop [Inhabited α] (s : Stack α) : Stack α :=
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{ vals := s.vals.pop .. s }
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def modify [Inhabited α] (s : Stack α) (f : α → α) : Stack α :=
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{ vals := s.vals.modify (s.vals.size-1) f .. s }
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end Stack
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