b5122b6a7b
This change * moves `termination_by` and `decreasing_by` next to the function they apply to * simplify the syntax of `termination_by` * apply the `decreasing_by` goal to all goals at once, for better interactive use. See the section in `RELEASES.md` for more details and migration advise. This is a hard breaking change, requiring developers to touch every `termination_by` in their code base. We decided to still do it as a hard-breaking change, because supporting both old and new syntax at the same time would be non-trivial, and not save that much. Moreover, this requires changes to some metaprograms that developers might have written, and supporting both syntaxes at the same time would make _their_ migration harder.
14 lines
583 B
Text
14 lines
583 B
Text
def List.bubblesort [LT α] [DecidableRel (· < · : α → α → Prop)] (l : List α) : {l' : List α // l.length = l'.length} :=
|
||
match l with
|
||
| [] => ⟨[], rfl⟩
|
||
| x :: xs =>
|
||
match bubblesort xs with
|
||
| ⟨[], h⟩ => ⟨[x], by simp[h]⟩
|
||
| ⟨y :: ys, h⟩ =>
|
||
if y < x then
|
||
have : Nat.succ (length ys) < Nat.succ (length xs) := by rw [h, List.length_cons]; apply Nat.lt_succ_self
|
||
let ⟨zs, he⟩ := bubblesort (x :: ys)
|
||
⟨y :: zs, by simp[h, ← he]⟩
|
||
else
|
||
⟨x :: y :: ys, by simp[h]⟩
|
||
termination_by l.length
|