lean4-htt/tests/lean/run/ack.lean
Leonardo de Moura 068cc700d8 test: ackermann
2022-01-11 15:03:07 -08:00

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def ack : Nat → Nat → Nat
| 0, y => y+1
| x+1, 0 => ack x 1
| x+1, y+1 => ack x (ack (x+1) y)
termination_by' PSigma.lex sizeOfWFRel (fun _ => sizeOfWFRel)