lean4-htt/tests/lean/run/wfrecUnary.lean
Leonardo de Moura 381f66428a chore: use termination_by'
We are going to define a higher level syntax for `termination_by`.
2022-01-11 15:00:53 -08:00

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def f (n : Nat) : Nat :=
if h : n = 0 then
1
else
2 * f (n-1)
termination_by' measure id
decreasing_by
simp [measure, id, invImage, InvImage, Nat.lt_wfRel]
apply Nat.pred_lt h