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