54 lines
1.6 KiB
Text
54 lines
1.6 KiB
Text
def step (state: Nat): Option Nat :=
|
|
if state = 0 then none else some (state - 1)
|
|
|
|
set_option linter.unusedVariables false
|
|
|
|
def countdown (state: Nat) :=
|
|
match h: step state with
|
|
| none => [state]
|
|
| some newState => state :: countdown newState
|
|
termination_by state
|
|
decreasing_by sorry
|
|
|
|
/--
|
|
error: tactic 'split' failed, consider using `set_option trace.split.failure true`
|
|
state : Nat
|
|
p :
|
|
(match h : step state with
|
|
| none => [state]
|
|
| some newState => state :: countdown newState) ≠
|
|
[]
|
|
⊢ (match h : step state with
|
|
| none => [state]
|
|
| some newState => state :: countdown newState).head
|
|
p =
|
|
state
|
|
---
|
|
info: [split.failure] `split` tactic failed to generalize discriminant(s) at
|
|
match h : step state with
|
|
| none => [state]
|
|
| some newState => state :: countdown newState
|
|
resulting expression was not type correct
|
|
possible solution: generalize discriminant(s) manually before using `split`
|
|
-/
|
|
#guard_msgs in
|
|
example (state: Nat) (p : (match h : step state with
|
|
| none => [state]
|
|
| some newState => state :: countdown newState) ≠
|
|
[]): (match h : step state with
|
|
| none => [state]
|
|
| some newState => state :: countdown newState).head
|
|
p =
|
|
state := by
|
|
set_option trace.split.failure true in
|
|
split
|
|
|
|
example (state: Nat) (p : (match h : step state with
|
|
| none => [state]
|
|
| some newState => state :: countdown newState) ≠
|
|
[]): (match h : step state with
|
|
| none => [state]
|
|
| some newState => state :: countdown newState).head
|
|
p =
|
|
state := by
|
|
split at p <;> simp
|