lean4-htt/tests/elab/funinduction_ident.lean
Garmelon 08eb78a5b2
chore: switch to new test/bench suite (#12590)
This PR sets up the new integrated test/bench suite. It then migrates
all benchmarks and some related tests to the new suite. There's also
some documentation and some linting.

For now, a lot of the old tests are left alone so this PR doesn't become
even larger than it already is. Eventually, all tests should be migrated
to the new suite though so there isn't a confusing mix of two systems.
2026-02-25 13:51:53 +00:00

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-- We re-define these here to avoid stage0 complications
def map (f : α → β) : List α → List β
| [] => []
| a::as => f a :: map f as
def zipWith (f : α → β → γ) : (xs : List α) → (ys : List β) → List γ
| x::xs, y::ys => f x y :: zipWith f xs ys
| _, _ => []
def append : (xs ys : List α) → List α
| [], bs => bs
| a::as, bs => a :: append as bs
namespace ListEx
theorem map_id (xs : List α) : map id xs = xs := by
fun_induction map <;> simp_all only [id]
-- This would work with the non-unfolding functional induction lemma, because there the function
-- argument to `map` is `.dropped`. But since we use the unfolding lemma it doesn't anymore:
/--
error: Found more than one suitable call of `map` in the goal. Please include the desired arguments.
-/
#guard_msgs in
theorem map_map (f : α → β) (g : β → γ) xs :
map g (map f xs) = map (g ∘ f) xs := by
fun_induction map <;> simp_all only [map, Function.comp]
-- With `set_option tactic.fun_induction.unfolding false` this works, because the function
-- argument to `map` is ignored when checking for a unique suitable call.
theorem map_map' (f : α → β) (g : β → γ) xs :
map g (map f xs) = map (g ∘ f) xs := by
set_option tactic.fun_induction.unfolding false in
fun_induction map <;> simp_all only [map, Function.comp]
-- This should genuinely not work, but have a good error message
/--
error: Found more than one suitable call of `append` in the goal. Please include the desired arguments.
-/
#guard_msgs in
theorem append_assoc :
append xs (append ys zs) = append (append xs ys) zs := by
fun_induction append <;> simp_all only [append]
end ListEx
namespace Ex1
variable (P : Nat → Prop)
def ackermann : (Nat × Nat) → Nat
| (0, m) => m + 1
| (n+1, 0) => ackermann (n, 1)
| (n+1, m+1) => ackermann (n, ackermann (n + 1, m))
termination_by p => p
/--
error: Failed: `fail` tactic was invoked
case case1
P : Nat → Prop
m✝ : Nat
⊢ P (m✝ + 1)
case case2
P : Nat → Prop
n✝ : Nat
ih1✝ : P (ackermann (n✝, 1))
⊢ P (ackermann (n✝, 1))
case case3
P : Nat → Prop
n✝ m✝ : Nat
ih2✝ : P (ackermann (n✝ + 1, m✝))
ih1✝ : P (ackermann (n✝, ackermann (n✝ + 1, m✝)))
⊢ P (ackermann (n✝, ackermann (n✝ + 1, m✝)))
-/
#guard_msgs in
example : P (ackermann p) := by
fun_induction ackermann
fail
/--
error: Failed: `fail` tactic was invoked
case case1
P : Nat → Prop
m✝ : Nat
⊢ P (m✝ + 1)
case case2
P : Nat → Prop
n✝ : Nat
⊢ P (ackermann (n✝, 1))
case case3
P : Nat → Prop
n✝ m✝ : Nat
⊢ P (ackermann (n✝, ackermann (n✝ + 1, m✝)))
-/
#guard_msgs in
example : P (ackermann p) := by
fun_cases ackermann
fail
/-- error: Could not find suitable call of `ackermann` in the goal -/
#guard_msgs in
example : P (ackermann (n, m)) := by
fun_induction ackermann
end Ex1
namespace Ex2
variable (P : Nat → Prop)
def ackermann : Nat → Nat → Nat
| 0, m => m + 1
| n+1, 0 => ackermann n 1
| n+1, m+1 => ackermann n (ackermann (n + 1) m)
termination_by n m => (n, m)
/--
error: unsolved goals
case case1
P : Nat → Prop
m✝ : Nat
⊢ P (m✝ + 1)
case case2
P : Nat → Prop
n✝ : Nat
ih1✝ : P (ackermann n✝ 1)
⊢ P (ackermann n✝ 1)
case case3
P : Nat → Prop
n✝ m✝ : Nat
ih2✝ : P (ackermann (n✝ + 1) m✝)
ih1✝ : P (ackermann n✝ (ackermann (n✝ + 1) m✝))
⊢ P (ackermann n✝ (ackermann (n✝ + 1) m✝))
-/
#guard_msgs in
example : P (ackermann n m) := by
fun_induction ackermann
end Ex2
namespace Ex3
variable (P : List α → Prop)
def ackermann {α} (inc : List α) : List α → List α → List α
| [], ms => ms ++ inc
| _::ns, [] => ackermann inc ns inc
| n::ns, _::ms => ackermann inc ns (ackermann inc (n::ns) ms)
termination_by ns ms => (ns, ms)
/--
error: unsolved goals
case case1
α : Type u_1
P : List α → Prop
inc ms✝ : List α
⊢ P (ms✝ ++ inc)
case case2
α : Type u_1
P : List α → Prop
inc : List α
head✝ : α
ns✝ : List α
ih1✝ : P (ackermann inc ns✝ inc)
⊢ P (ackermann inc ns✝ inc)
case case3
α : Type u_1
P : List α → Prop
inc : List α
n✝ : α
ns✝ : List α
head✝ : α
ms✝ : List α
ih2✝ : P (ackermann inc (n✝ :: ns✝) ms✝)
ih1✝ : P (ackermann inc ns✝ (ackermann inc (n✝ :: ns✝) ms✝))
⊢ P (ackermann inc ns✝ (ackermann inc (n✝ :: ns✝) ms✝))
-/
#guard_msgs in
example : P (ackermann inc n m) := by
fun_induction ackermann
end Ex3
namespace Structural
variable (P : Nat → Prop)
def fib : Nat → Nat
| 0 => 0
| 1 => 1
| n+2 => fib n + fib (n+1)
termination_by structural x => x
/--
error: Failed: `fail` tactic was invoked
case case1
P : Nat → Prop
⊢ P 0
case case2
P : Nat → Prop
⊢ P 1
case case3
P : Nat → Prop
n✝ : Nat
ih2✝ : P (fib n✝)
ih1✝ : P (fib (n✝ + 1))
⊢ P (fib n✝ + fib (n✝ + 1))
-/
#guard_msgs in
example : P (fib n) := by
fun_induction fib
fail
/-- error: Could not find suitable call of `fib` in the goal -/
#guard_msgs in
example : n ≤ fib (n + 2) := by
fun_induction fib
end Structural
namespace StructuralWithOmittedParam
variable (P : Nat → Prop)
variable (inc : Nat)
def fib : Nat → Nat
| 0 => 0
| 1 => inc
| n+2 => fib n + fib (n+1)
termination_by structural x => x
/--
info: StructuralWithOmittedParam.fib.induct (motive : Nat → Prop) (case1 : motive 0) (case2 : motive 1)
(case3 : ∀ (n : Nat), motive n → motive (n + 1) → motive n.succ.succ) (a✝ : Nat) : motive a✝
-/
#guard_msgs in
#check fib.induct -- NB: No inc showing up
/--
error: Failed: `fail` tactic was invoked
case case1
P : Nat → Prop
inc : Nat
⊢ P 0
case case2
P : Nat → Prop
inc : Nat
⊢ P 2
case case3
P : Nat → Prop
inc n✝ : Nat
ih2✝ : P (fib 2 n✝)
ih1✝ : P (fib 2 (n✝ + 1))
⊢ P (fib 2 n✝ + fib 2 (n✝ + 1))
-/
#guard_msgs in
example : P (fib 2 n) := by
fun_induction fib
fail
end StructuralWithOmittedParam
namespace StructuralIndices
-- Testing recursion on an indexed data type
inductive Finn : Nat → Type where
| fzero : {n : Nat} → Finn n
| fsucc : {n : Nat} → Finn n → Finn (n+1)
def Finn.min (x : Bool) {n : Nat} (m : Nat) : Finn n → (f : Finn n) → Finn n
| fzero, _ => fzero
| _, fzero => fzero
| fsucc i, fsucc j => fsucc (Finn.min (not x) (m + 1) i j)
termination_by structural i => i
def Finn.min' (x : Bool) {n : Nat} (m : Nat) : Finn n → (f : Finn n) → Finn n
| fzero, _ => fzero
| _, fzero => fzero
| fsucc i, fsucc j => fsucc (Finn.min' (not x) (m + 1) i j)
termination_by structural _ j => j
def Finn.min'' (x : Bool) {n : Nat} (m : Nat) : Finn n → (f : Finn n) → Finn n
| fzero, _ => fzero
| _, fzero => fzero
| fsucc i, fsucc j => fsucc (Finn.min'' (not x) (m + 1) i j)
termination_by structural n
def Finn.le : Finn n → Finn n → Bool
| fzero, _ => true
| _, fzero => false
| fsucc i, fsucc j => Finn.le i j
theorem Finn.min_le_right₀ : (Finn.min x m i j).le j := by
induction x, m, i, j using @Finn.min.induct <;> simp_all [Finn.min, Finn.le]
theorem Finn.min_le_right : (Finn.min x m i j).le j := by
fun_induction Finn.min <;> simp_all [Finn.min, Finn.le]
theorem Finn.min_le_right' : (Finn.min' x m i j).le j := by
fun_induction Finn.min' <;> simp_all [Finn.min', Finn.le]
theorem Finn.min_le_right'' : (Finn.min'' x m i j).le j := by
fun_induction Finn.min'' <;> simp_all [Finn.min'', Finn.le]
end StructuralIndices
namespace Nonrec
def foo := 1
/-- error: No functional induction theorem for `foo`, or function is mutually recursive -/
#guard_msgs in
example : True := by
fun_induction foo
end Nonrec
namespace Mutual
inductive Tree (α : Type u) : Type u where
| node : α → (Bool → List (Tree α)) → Tree α
-- Recursion over nested inductive
mutual
def Tree.size : Tree α → Nat
| .node _ tsf => 1 + size_aux (tsf true) + size_aux (tsf false)
termination_by structural t => t
def Tree.size_aux : List (Tree α) → Nat
| [] => 0
| t :: ts => size t + size_aux ts
end
/-- error: No functional induction theorem for `Tree.size`, or function is mutually recursive -/
#guard_msgs in
example (t : Tree α) : True := by
fun_induction Tree.size
end Mutual