a888b21bce
Fixes issue reported at https://leanprover.zulipchat.com/#narrow/stream/270676-lean4/topic/.28libc.2B.2Babi.29.20lean.3A.3Aexception.3A.20incomplete.20case/near/287839995
28 lines
773 B
Text
28 lines
773 B
Text
inductive FinInt: Nat → Type :=
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| nil: FinInt 0
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| next: Bool → FinInt n → FinInt (n+1)
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deriving DecidableEq
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def zero (sz: Nat): FinInt sz :=
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match sz with
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| 0 => .nil
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| sz+1 => .next false (zero sz)
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inductive Pair :=
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| mk (sz: Nat) (lhs rhs: FinInt sz)
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def makePair?: (n m: (sz: Nat) × FinInt sz) → Option Pair
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| ⟨sz, lhs⟩, ⟨sz', rhs⟩ =>
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if EQ: true /\ sz = sz' then
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have rhs' : FinInt sz := by {
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cases EQ;
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case intro left right =>
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simp [right];
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exact rhs;
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};
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some (Pair.mk sz lhs rhs')
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else none
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def usePair: Pair → Bool := fun ⟨sz, lhs, rhs⟩ => lhs = rhs
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#eval (makePair? ⟨8, zero 8⟩ ⟨8, zero 8⟩).map usePair
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