theorem
proved
term proof
lt_iff_succ_le
show as:
view Lean formalization →
formal statement (Lean)
356theorem lt_iff_succ_le {n m : LogicNat} : n < m ↔ succ n ≤ m := by
proof body
Term-mode proof.
357 constructor
358 · rintro ⟨k, hk⟩
359 refine ⟨k, ?_⟩
360 show succ n + k = m
361 rw [succ_add]
362 show succ (n + k) = m
363 rw [← add_succ]
364 -- need n + succ k = m, but we have n + succ k = m via hk; succ_add transforms
365 -- Wait: hk : n + succ k = m, and succ (n + k) = n + succ k by add_succ. So succ (n + k) = m.
366 exact hk
367 · rintro ⟨k, hk⟩
368 refine ⟨k, ?_⟩
369 show n + succ k = m
370 rw [add_succ]
371 show succ (n + k) = m
372 rw [← succ_add]
373 exact hk
374