197bc6cb66
This PR redefines `String` to be the type of byte arrays `b` for which `b.IsValidUtf8`. This moves the data model of strings much closer to the actual data representation at runtime. In the near future, we will - provide variants of `String.Pos` and `Substring` that only allow for valid positions - redefine all `String` functions to be much closer to their C++ implementations In the near-to-medium future we will then provide comprehensive verification of `String` based on these refactors.
42 lines
1.4 KiB
Text
42 lines
1.4 KiB
Text
/--
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info: Option.map.fun_cases.{u_1} {α : Type u_1} (motive : Option α → Prop) (case1 : ∀ (x : α), motive (some x))
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(case2 : motive none) (x✝ : Option α) : motive x✝
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-/
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#guard_msgs(pass trace, all) in
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#check Option.map.fun_cases
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example (x : Option Nat) (f : Nat → Nat) : (x.map f).isSome = x.isSome := by
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cases x using Option.map.fun_cases
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case case1 x => simp
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case case2 => simp
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/--
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info: List.map.fun_cases.{u_1} {α : Type u_1} (motive : List α → Prop) (case1 : motive [])
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(case2 : ∀ (head : α) (as : List α), motive (head :: as)) (x✝ : List α) : motive x✝
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-/
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#guard_msgs in
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#check List.map.fun_cases
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/--
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info: List.find?.fun_cases.{u} {α : Type u} (p : α → Bool) (motive : List α → Prop) (case1 : motive [])
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(case2 : ∀ (a : α) (as : List α), p a = true → motive (a :: as))
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(case3 : ∀ (a : α) (as : List α), p a = false → motive (a :: as)) (x✝ : List α) : motive x✝
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-/
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#guard_msgs in
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#check List.find?.fun_cases
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-- This tests shows that its not so easy to post-hoc recognize that `x` could be a parameter, but
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-- `y` should be a target of the `fun_cases` principle (or the other way around)
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def areTheseTargetsUnchanged (x y : Nat) : Bool :=
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if _ : x = y then
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true
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else
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false
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/--
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info: areTheseTargetsUnchanged.fun_cases (x y : Nat) (motive : Prop) (case1 : x = y → motive) (case2 : ¬x = y → motive) :
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motive
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-/
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#guard_msgs in
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#check areTheseTargetsUnchanged.fun_cases
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