14 lines
687 B
Text
14 lines
687 B
Text
-- Print a nat using well-founded recursion
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def natPrintAux (n : Nat) (sink : List Char) : List Char :=
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if h0 : n < 10
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then (n.digitChar :: sink)
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else natPrintAux (n / 10) (Nat.digitChar (n % 10) :: sink)
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termination_by' measure (fun ⟨n, _⟩ => n)
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decreasing_by sorry
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set_option maxRecDepth 100 -- default takes ages in debug mode and triggers stack space threshold
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-- I meant to write `simp only [natPrintAux]`, but accidentally referenced the current theorem
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theorem natPrintAux_eq (n : Nat) (sink : List Char) :
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natPrintAux n sink = if n < 10 then (n.digitChar :: sink) else natPrintAux (n / 10) (Nat.digitChar (n % 10) :: sink) := by
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simp only [natPrintAux_eq]
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