41a2e9af19
This PR makes functions defined by well-founded recursion use an `opaque` well-founded proof by default. This reliably prevents kernel reduction of such definitions and proofs, which tends to be prohibitively slow (fixes #2171), and which regularly causes hard-to-debug kernel type-checking failures. This changes renders `unseal` ineffective for such definitions. To avoid the opaque proof, annotate the function definition with `@[semireducible]`.
22 lines
450 B
Text
22 lines
450 B
Text
def numChars (s : String) : Nat :=
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go s.iter
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where
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go (i : String.Iterator) : Nat :=
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if h : i.hasNext then
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go i.next + 1
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else
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0
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#guard numChars "aαc" == 3
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example : numChars "aαc" = 3 := by native_decide
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def numChars2 (s : String) : Nat :=
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go s.iter
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where
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go (i : String.Iterator) : Nat :=
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match h : i.hasNext with
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| true => go i.next + 1
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| false => 0
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example : numChars2 "aαc" = 3 := by native_decide
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