79659457fb
This PR reduces the usage of `String.length` in our codebase. This is just the first step of many towards eliminating `String.length`.
31 lines
798 B
Text
31 lines
798 B
Text
/-
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Copyright (c) 2026 Lean FRO, LLC. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Markus Himmel
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-/
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module
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prelude
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public import Init.Data.String.Length
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public import Init.Data.String.Modify
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import Init.Data.String.Lemmas.Modify
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import Init.Data.String.Lemmas.Intercalate
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public section
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namespace String
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@[simp]
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theorem length_eq_zero_iff {s : String} : s.length = 0 ↔ s = "" := by
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simp [← length_toList]
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@[simp]
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theorem length_map {f : Char → Char} {s : String} : (s.map f).length = s.length := by
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simp [← length_toList]
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@[simp]
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theorem length_join {l : List String} : (String.join l).length = (l.map String.length).sum := by
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simp only [← length_toList, toList_join, List.length_flatMap]
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simp [length_toList]
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end String
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