# Sums and products from lists #

This file provides basic results about List.prod, List.sum, which calculate the product and sum of elements of a list and List.alternatingProd, List.alternatingSum, their alternating counterparts.

def List.sum {α : Type u_8} [Add α] [Zero α] :
List αα

Sum of a list.

List.sum [a, b, c] = ((0 + a) + b) + c

Equations
Instances For
def List.prod {α : Type u_8} [Mul α] [One α] :
List αα

Product of a list.

List.prod [a, b, c] = ((1 * a) * b) * c

Equations
Instances For
def List.alternatingSum {G : Type u_8} [Zero G] [Add G] [Neg G] :
List GG

The alternating sum of a list.

Equations
• [].alternatingSum = 0
• [g].alternatingSum = g
• (g :: h :: t).alternatingSum = g + -h + t.alternatingSum
Instances For
def List.alternatingProd {G : Type u_8} [One G] [Mul G] [Inv G] :
List GG

The alternating product of a list.

Equations
• [].alternatingProd = 1
• [g].alternatingProd = g
• (g :: h :: t).alternatingProd = g * h⁻¹ * t.alternatingProd
Instances For
@[simp]
theorem List.sum_nil {M : Type u_4} [] :
[].sum = 0
@[simp]
theorem List.prod_nil {M : Type u_4} [] :
[].prod = 1
theorem List.sum_singleton {M : Type u_4} [] {a : M} :
[a].sum = a
theorem List.prod_singleton {M : Type u_4} [] {a : M} :
[a].prod = a
@[simp]
theorem List.sum_zero_cons {M : Type u_4} [] {l : List M} :
(0 :: l).sum = l.sum
@[simp]
theorem List.prod_one_cons {M : Type u_4} [] {l : List M} :
(1 :: l).prod = l.prod
theorem List.sum_map_zero {ι : Type u_1} {M : Type u_4} [] {l : List ι} :
(List.map (fun (x : ι) => 0) l).sum = 0
theorem List.prod_map_one {ι : Type u_1} {M : Type u_4} [] {l : List ι} :
(List.map (fun (x : ι) => 1) l).prod = 1
@[simp]
theorem List.sum_cons {M : Type u_4} [] {l : List M} {a : M} :
(a :: l).sum = a + l.sum
@[simp]
theorem List.prod_cons {M : Type u_4} [] {l : List M} {a : M} :
(a :: l).prod = a * l.prod
theorem List.sum_induction {M : Type u_4} [] {l : List M} (p : MProp) (hom : ∀ (a b : M), p ap bp (a + b)) (unit : p 0) (base : xl, p x) :
p l.sum
theorem List.prod_induction {M : Type u_4} [] {l : List M} (p : MProp) (hom : ∀ (a b : M), p ap bp (a * b)) (unit : p 1) (base : xl, p x) :
p l.prod
@[simp]
theorem List.sum_append {M : Type u_4} [] {l₁ : List M} {l₂ : List M} :
(l₁ ++ l₂).sum = l₁.sum + l₂.sum
@[simp]
theorem List.prod_append {M : Type u_4} [] {l₁ : List M} {l₂ : List M} :
(l₁ ++ l₂).prod = l₁.prod * l₂.prod
theorem List.sum_concat {M : Type u_4} [] {l : List M} {a : M} :
(l.concat a).sum = l.sum + a
theorem List.prod_concat {M : Type u_4} [] {l : List M} {a : M} :
(l.concat a).prod = l.prod * a
@[simp]
theorem List.sum_join {M : Type u_4} [] {l : List (List M)} :
l.join.sum = (List.map List.sum l).sum
@[simp]
theorem List.prod_join {M : Type u_4} [] {l : List (List M)} :
l.join.prod = (List.map List.prod l).prod
theorem List.sum_eq_foldr {M : Type u_4} [] {l : List M} :
l.sum = List.foldr (fun (x x_1 : M) => x + x_1) 0 l
abbrev List.sum_eq_foldr.match_1 {M : Type u_1} (motive : List MProp) :
∀ (x : List M), (Unitmotive [])(∀ (a : M) (l : List M), motive (a :: l))motive x
Equations
• =
Instances For
theorem List.prod_eq_foldr {M : Type u_4} [] {l : List M} :
l.prod = List.foldr (fun (x x_1 : M) => x * x_1) 1 l
@[simp]
theorem List.sum_replicate {M : Type u_4} [] (n : ) (a : M) :
().sum = n a
@[simp]
theorem List.prod_replicate {M : Type u_4} [] (n : ) (a : M) :
().prod = a ^ n
theorem List.sum_eq_card_nsmul {M : Type u_4} [] (l : List M) (m : M) (h : xl, x = m) :
l.sum = l.length m
theorem List.prod_eq_pow_card {M : Type u_4} [] (l : List M) (m : M) (h : xl, x = m) :
l.prod = m ^ l.length
theorem List.sum_hom_rel {ι : Type u_1} {M : Type u_4} {N : Type u_5} [] [] (l : List ι) {r : MNProp} {f : ιM} {g : ιN} (h₁ : r 0 0) (h₂ : ∀ ⦃i : ι⦄ ⦃a : M⦄ ⦃b : N⦄, r a br (f i + a) (g i + b)) :
r (List.map f l).sum (List.map g l).sum
theorem List.prod_hom_rel {ι : Type u_1} {M : Type u_4} {N : Type u_5} [] [] (l : List ι) {r : MNProp} {f : ιM} {g : ιN} (h₁ : r 1 1) (h₂ : ∀ ⦃i : ι⦄ ⦃a : M⦄ ⦃b : N⦄, r a br (f i * a) (g i * b)) :
r (List.map f l).prod (List.map g l).prod
theorem List.rel_sum {M : Type u_4} {N : Type u_5} [] [] {R : MNProp} (h : R 0 0) (hf : (R R R) (fun (x x_1 : M) => x + x_1) fun (x x_1 : N) => x + x_1) :
() List.sum List.sum
theorem List.rel_prod {M : Type u_4} {N : Type u_5} [] [] {R : MNProp} (h : R 1 1) (hf : (R R R) (fun (x x_1 : M) => x * x_1) fun (x x_1 : N) => x * x_1) :
() List.prod List.prod
theorem List.sum_hom {M : Type u_4} {N : Type u_5} [] [] (l : List M) {F : Type u_8} [FunLike F M N] [] (f : F) :
(List.map (f) l).sum = f l.sum
theorem List.prod_hom {M : Type u_4} {N : Type u_5} [] [] (l : List M) {F : Type u_8} [FunLike F M N] [] (f : F) :
(List.map (f) l).prod = f l.prod
theorem List.sum_hom₂ {ι : Type u_1} {M : Type u_4} {N : Type u_5} {P : Type u_6} [] [] [] (l : List ι) (f : MNP) (hf : ∀ (a b : M) (c d : N), f (a + b) (c + d) = f a c + f b d) (hf' : f 0 0 = 0) (f₁ : ιM) (f₂ : ιN) :
(List.map (fun (i : ι) => f (f₁ i) (f₂ i)) l).sum = f (List.map f₁ l).sum (List.map f₂ l).sum
theorem List.prod_hom₂ {ι : Type u_1} {M : Type u_4} {N : Type u_5} {P : Type u_6} [] [] [] (l : List ι) (f : MNP) (hf : ∀ (a b : M) (c d : N), f (a * b) (c * d) = f a c * f b d) (hf' : f 1 1 = 1) (f₁ : ιM) (f₂ : ιN) :
(List.map (fun (i : ι) => f (f₁ i) (f₂ i)) l).prod = f (List.map f₁ l).prod (List.map f₂ l).prod
@[simp]
theorem List.sum_map_add {ι : Type u_1} {α : Type u_8} [] {l : List ι} {f : ια} {g : ια} :
(List.map (fun (i : ι) => f i + g i) l).sum = (List.map f l).sum + (List.map g l).sum
@[simp]
theorem List.prod_map_mul {ι : Type u_1} {α : Type u_8} [] {l : List ι} {f : ια} {g : ια} :
(List.map (fun (i : ι) => f i * g i) l).prod = (List.map f l).prod * (List.map g l).prod
theorem List.sum_map_hom {ι : Type u_1} {M : Type u_4} {N : Type u_5} [] [] (L : List ι) (f : ιM) {G : Type u_8} [FunLike G M N] [] (g : G) :
(List.map (g f) L).sum = g (List.map f L).sum
theorem List.prod_map_hom {ι : Type u_1} {M : Type u_4} {N : Type u_5} [] [] (L : List ι) (f : ιM) {G : Type u_8} [FunLike G M N] [] (g : G) :
(List.map (g f) L).prod = g (List.map f L).prod
theorem List.sum_isAddUnit {M : Type u_4} [] {L : List M} :
abbrev List.sum_isAddUnit.match_1 {M : Type u_1} [] (motive : (x : List M) → (mx, )Prop) :
∀ (x : List M) (x_1 : mx, ), (∀ (x : m[], ), motive [] x)(∀ (h : M) (t : List M) (u : mh :: t, ), motive (h :: t) u)motive x x_1
Equations
• =
Instances For
theorem List.prod_isUnit {M : Type u_4} [] {L : List M} :
(mL, )IsUnit L.prod
theorem List.sum_isAddUnit_iff {α : Type u_8} [] {L : List α} :
theorem List.prod_isUnit_iff {α : Type u_8} [] {L : List α} :
IsUnit L.prod mL,
@[simp]
theorem List.sum_take_add_sum_drop {M : Type u_4} [] (L : List M) (i : ) :
().sum + ().sum = L.sum
abbrev List.sum_take_add_sum_drop.match_1 {M : Type u_1} (motive : List M) :
∀ (x : List M) (x_1 : ), (∀ (i : ), motive [] i)(∀ (L : List M), motive L 0)(∀ (h : M) (t : List M) (n : ), motive (h :: t) n.succ)motive x x_1
Equations
• =
Instances For
@[simp]
theorem List.prod_take_mul_prod_drop {M : Type u_4} [] (L : List M) (i : ) :
().prod * ().prod = L.prod
@[simp]
theorem List.sum_take_succ {M : Type u_4} [] (L : List M) (i : ) (p : i < L.length) :
(List.take (i + 1) L).sum = ().sum + L.get i, p
abbrev List.sum_take_succ.match_1 {M : Type u_1} (motive : (x : List M) → (x_1 : ) → x_1 < x.lengthProp) :
∀ (x : List M) (x_1 : ) (x_2 : x_1 < x.length), (∀ (i : ) (p : i < [].length), motive [] i p)(∀ (h : M) (t : List M) (x : 0 < (h :: t).length), motive (h :: t) 0 x)(∀ (h : M) (t : List M) (n : ) (p : n + 1 < (h :: t).length), motive (h :: t) n.succ p)motive x x_1 x_2
Equations
• =
Instances For
@[simp]
theorem List.prod_take_succ {M : Type u_4} [] (L : List M) (i : ) (p : i < L.length) :
(List.take (i + 1) L).prod = ().prod * L.get i, p
theorem List.length_pos_of_sum_ne_zero {M : Type u_4} [] (L : List M) (h : L.sum 0) :
0 < L.length

A list with sum not zero must have positive length.

theorem List.length_pos_of_prod_ne_one {M : Type u_4} [] (L : List M) (h : L.prod 1) :
0 < L.length

A list with product not one must have positive length.

theorem List.length_pos_of_sum_pos {M : Type u_4} [] [] (L : List M) (h : 0 < L.sum) :
0 < L.length

A list with positive sum must have positive length.

theorem List.length_pos_of_one_lt_prod {M : Type u_4} [] [] (L : List M) (h : 1 < L.prod) :
0 < L.length

A list with product greater than one must have positive length.

theorem List.length_pos_of_sum_neg {M : Type u_4} [] [] (L : List M) (h : L.sum < 0) :
0 < L.length

A list with negative sum must have positive length.

theorem List.length_pos_of_prod_lt_one {M : Type u_4} [] [] (L : List M) (h : L.prod < 1) :
0 < L.length

A list with product less than one must have positive length.

abbrev List.sum_set.match_1 {M : Type u_1} (motive : List MMProp) :
∀ (x : List M) (x_1 : ) (x_2 : M), (∀ (x : M) (xs : List M) (a : M), motive (x :: xs) 0 a)(∀ (x : M) (xs : List M) (i : ) (a : M), motive (x :: xs) i.succ a)(∀ (x : ) (x_3 : M), motive [] x x_3)motive x x_1 x_2
Equations
• =
Instances For
theorem List.sum_set {M : Type u_4} [] (L : List M) (n : ) (a : M) :
(L.set n a).sum = (().sum + if n < L.length then a else 0) + (List.drop (n + 1) L).sum
theorem List.prod_set {M : Type u_4} [] (L : List M) (n : ) (a : M) :
(L.set n a).prod = (().prod * if n < L.length then a else 1) * (List.drop (n + 1) L).prod
theorem List.get?_zero_add_tail_sum {M : Type u_4} [] (l : List M) :
(l.get? 0).getD 0 + l.tail.sum = l.sum

We'd like to state this as L.headI + L.tail.sum = L.sum, but because L.headI relies on an inhabited instance to return a garbage value on the empty list, this is not possible. Instead, we write the statement in terms of (L.get? 0).getD 0.

theorem List.get?_zero_mul_tail_prod {M : Type u_4} [] (l : List M) :
(l.get? 0).getD 1 * l.tail.prod = l.prod

We'd like to state this as L.headI * L.tail.prod = L.prod, but because L.headI relies on an inhabited instance to return a garbage value on the empty list, this is not possible. Instead, we write the statement in terms of (L.get? 0).getD 1.

theorem List.headI_add_tail_sum_of_ne_nil {M : Type u_4} [] [] (l : List M) (h : l []) :

Same as get?_zero_add_tail_sum, but avoiding the List.headI garbage complication by requiring the list to be nonempty.

theorem List.headI_mul_tail_prod_of_ne_nil {M : Type u_4} [] [] (l : List M) (h : l []) :

Same as get?_zero_mul_tail_prod, but avoiding the List.headI garbage complication by requiring the list to be nonempty.

theorem AddCommute.list_sum_right {M : Type u_4} [] (l : List M) (y : M) (h : xl, ) :
theorem Commute.list_prod_right {M : Type u_4} [] (l : List M) (y : M) (h : xl, Commute y x) :
Commute y l.prod
theorem AddCommute.list_sum_left {M : Type u_4} [] (l : List M) (y : M) (h : xl, ) :
theorem Commute.list_prod_left {M : Type u_4} [] (l : List M) (y : M) (h : xl, Commute x y) :
Commute l.prod y
theorem List.sum_range_succ {M : Type u_4} [] (f : M) (n : ) :
(List.map f (List.range n.succ)).sum = (List.map f ()).sum + f n
theorem List.prod_range_succ {M : Type u_4} [] (f : M) (n : ) :
(List.map f (List.range n.succ)).prod = (List.map f ()).prod * f n
theorem List.sum_range_succ' {M : Type u_4} [] (f : M) (n : ) :
(List.map f (List.range n.succ)).sum = f 0 + (List.map (fun (i : ) => f i.succ) ()).sum

A variant of sum_range_succ which pulls off the first term in the sum rather than the last.

theorem List.prod_range_succ' {M : Type u_4} [] (f : M) (n : ) :
(List.map f (List.range n.succ)).prod = f 0 * (List.map (fun (i : ) => f i.succ) ()).prod

A variant of prod_range_succ which pulls off the first term in the product rather than the last.

theorem List.sum_eq_zero {M : Type u_4} [] {l : List M} (hl : xl, x = 0) :
l.sum = 0
theorem List.prod_eq_one {M : Type u_4} [] {l : List M} (hl : xl, x = 1) :
l.prod = 1
theorem List.exists_mem_ne_zero_of_sum_ne_zero {M : Type u_4} [] {l : List M} (h : l.sum 0) :
xl, x 0
theorem List.exists_mem_ne_one_of_prod_ne_one {M : Type u_4} [] {l : List M} (h : l.prod 1) :
xl, x 1
theorem List.sum_erase_of_comm {M : Type u_4} [] {l : List M} {a : M} [] (ha : a l) (comm : xl, yl, x + y = y + x) :
a + (l.erase a).sum = l.sum
theorem List.prod_erase_of_comm {M : Type u_4} [] {l : List M} {a : M} [] (ha : a l) (comm : xl, yl, x * y = y * x) :
a * (l.erase a).prod = l.prod
theorem List.sum_map_eq_nsmul_single {α : Type u_2} {M : Type u_4} [] [] {l : List α} (a : α) (f : αM) (hf : ∀ (a' : α), a' aa' lf a' = 0) :
(List.map f l).sum = f a
theorem List.prod_map_eq_pow_single {α : Type u_2} {M : Type u_4} [] [] {l : List α} (a : α) (f : αM) (hf : ∀ (a' : α), a' aa' lf a' = 1) :
(List.map f l).prod = f a ^
theorem List.sum_eq_nsmul_single {M : Type u_4} [] {l : List M} [] (a : M) (h : ∀ (a' : M), a' aa' la' = 0) :
l.sum = a
theorem List.prod_eq_pow_single {M : Type u_4} [] {l : List M} [] (a : M) (h : ∀ (a' : M), a' aa' la' = 1) :
l.prod = a ^
theorem List.Perm.sum_eq' {M : Type u_4} [] {l₁ : List M} {l₂ : List M} (h : l₁.Perm l₂) (hc : List.Pairwise AddCommute l₁) :
l₁.sum = l₂.sum

If elements of a list additively commute with each other, then their sum does not depend on the order of elements.

theorem List.Perm.prod_eq' {M : Type u_4} [] {l₁ : List M} {l₂ : List M} (h : l₁.Perm l₂) (hc : List.Pairwise Commute l₁) :
l₁.prod = l₂.prod

If elements of a list commute with each other, then their product does not depend on the order of elements.

@[simp]
theorem List.sum_erase {M : Type u_4} [] {a : M} {l : List M} [] (ha : a l) :
a + (l.erase a).sum = l.sum
@[simp]
theorem List.prod_erase {M : Type u_4} [] {a : M} {l : List M} [] (ha : a l) :
a * (l.erase a).prod = l.prod
@[simp]
theorem List.sum_map_erase {α : Type u_2} {M : Type u_4} [] [] (f : αM) {a : α} {l : List α} :
a lf a + (List.map f (l.erase a)).sum = (List.map f l).sum
abbrev List.sum_map_erase.match_1 {α : Type u_1} {a : α} (motive : (x : List α) → a xProp) :
∀ (x : List α) (x_1 : a x), (∀ (b : α) (l : List α) (h : a b :: l), motive (b :: l) h)motive x x_1
Equations
• =
Instances For
@[simp]
theorem List.prod_map_erase {α : Type u_2} {M : Type u_4} [] [] (f : αM) {a : α} {l : List α} :
a lf a * (List.map f (l.erase a)).prod = (List.map f l).prod
theorem List.Perm.sum_eq {M : Type u_4} [] {l₁ : List M} {l₂ : List M} (h : l₁.Perm l₂) :
l₁.sum = l₂.sum
theorem List.Perm.prod_eq {M : Type u_4} [] {l₁ : List M} {l₂ : List M} (h : l₁.Perm l₂) :
l₁.prod = l₂.prod
theorem List.sum_reverse {M : Type u_4} [] (l : List M) :
l.reverse.sum = l.sum
theorem List.prod_reverse {M : Type u_4} [] (l : List M) :
l.reverse.prod = l.prod
theorem List.sum_add_sum_eq_sum_zipWith_add_sum_drop {M : Type u_4} [] (l : List M) (l' : List M) :
l.sum + l'.sum = (List.zipWith (fun (x x_1 : M) => x + x_1) l l').sum + (List.drop l'.length l).sum + (List.drop l.length l').sum
abbrev List.sum_add_sum_eq_sum_zipWith_add_sum_drop.match_1 {M : Type u_1} (motive : List MList MProp) :
∀ (x x_1 : List M), (∀ (ys : List M), motive [] ys)(∀ (xs : List M), motive xs [])(∀ (x : M) (xs : List M) (y : M) (ys : List M), motive (x :: xs) (y :: ys))motive x x_1
Equations
• =
Instances For
theorem List.prod_mul_prod_eq_prod_zipWith_mul_prod_drop {M : Type u_4} [] (l : List M) (l' : List M) :
l.prod * l'.prod = (List.zipWith (fun (x x_1 : M) => x * x_1) l l').prod * (List.drop l'.length l).prod * (List.drop l.length l').prod
theorem List.sum_add_sum_eq_sum_zipWith_of_length_eq {M : Type u_4} [] (l : List M) (l' : List M) (h : l.length = l'.length) :
l.sum + l'.sum = (List.zipWith (fun (x x_1 : M) => x + x_1) l l').sum
theorem List.prod_mul_prod_eq_prod_zipWith_of_length_eq {M : Type u_4} [] (l : List M) (l' : List M) (h : l.length = l'.length) :
l.prod * l'.prod = (List.zipWith (fun (x x_1 : M) => x * x_1) l l').prod
theorem List.eq_of_sum_take_eq {M : Type u_4} {L : List M} {L' : List M} (h : L.length = L'.length) (h' : iL.length, ().sum = (List.take i L').sum) :
L = L'
theorem List.eq_of_prod_take_eq {M : Type u_4} [] {L : List M} {L' : List M} (h : L.length = L'.length) (h' : iL.length, ().prod = (List.take i L').prod) :
L = L'
theorem List.sum_neg_reverse {G : Type u_7} [] (L : List G) :
-L.sum = (List.map (fun (x : G) => -x) L).reverse.sum

This is the List.sum version of add_neg_rev

theorem List.prod_inv_reverse {G : Type u_7} [] (L : List G) :
L.prod⁻¹ = (List.map (fun (x : G) => x⁻¹) L).reverse.prod

This is the List.prod version of mul_inv_rev

theorem List.sum_reverse_noncomm {G : Type u_7} [] (L : List G) :
L.reverse.sum = -(List.map (fun (x : G) => -x) L).sum

A non-commutative variant of List.sum_reverse

theorem List.prod_reverse_noncomm {G : Type u_7} [] (L : List G) :
L.reverse.prod = (List.map (fun (x : G) => x⁻¹) L).prod⁻¹

A non-commutative variant of List.prod_reverse

@[simp]
theorem List.sum_drop_succ {G : Type u_7} [] (L : List G) (i : ) (p : i < L.length) :
(List.drop (i + 1) L).sum = -L.get i, p + ().sum

Counterpart to List.sum_take_succ when we have a negation operation

@[simp]
theorem List.prod_drop_succ {G : Type u_7} [] (L : List G) (i : ) (p : i < L.length) :
(List.drop (i + 1) L).prod = (L.get i, p)⁻¹ * ().prod

Counterpart to List.prod_take_succ when we have an inverse operation

theorem List.sum_range_sub' {G : Type u_7} [] (n : ) (f : G) :
(List.map (fun (k : ) => f k - f (k + 1)) ()).sum = f 0 - f n

Cancellation of a telescoping sum.

theorem List.prod_range_div' {G : Type u_7} [] (n : ) (f : G) :
(List.map (fun (k : ) => f k / f (k + 1)) ()).prod = f 0 / f n

Cancellation of a telescoping product.

theorem List.prod_rotate_eq_one_of_prod_eq_one {G : Type u_7} [] {l : List G} :
l.prod = 1∀ (n : ), (l.rotate n).prod = 1
theorem List.sum_neg {G : Type u_7} [] (L : List G) :
-L.sum = (List.map (fun (x : G) => -x) L).sum

This is the List.sum version of add_neg

theorem List.prod_inv {G : Type u_7} [] (L : List G) :
L.prod⁻¹ = (List.map (fun (x : G) => x⁻¹) L).prod

This is the List.prod version of mul_inv

theorem List.sum_range_sub {G : Type u_7} [] (n : ) (f : G) :
(List.map (fun (k : ) => f (k + 1) - f k) ()).sum = f n - f 0

Cancellation of a telescoping sum.

theorem List.prod_range_div {G : Type u_7} [] (n : ) (f : G) :
(List.map (fun (k : ) => f (k + 1) / f k) ()).prod = f n / f 0

Cancellation of a telescoping product.

theorem List.sum_set' {G : Type u_7} [] (L : List G) (n : ) (a : G) :
(L.set n a).sum = L.sum + if hn : n < L.length then -L.get n, hn + a else 0

Alternative version of List.sum_set when the list is over a group

theorem List.prod_set' {G : Type u_7} [] (L : List G) (n : ) (a : G) :
(L.set n a).prod = L.prod * if hn : n < L.length then (L.get n, hn)⁻¹ * a else 1

Alternative version of List.prod_set when the list is over a group

theorem List.sum_const_nat (m : ) (n : ) :
().sum = m * n

Several lemmas about sum/head/tail for List ℕ. These are hard to generalize well, as they rely on the fact that default ℕ = 0. If desired, we could add a class stating that default = 0.

This relies on default ℕ = 0.

theorem List.headI_le_sum (L : ) :

This relies on default ℕ = 0.

theorem List.tail_sum (L : ) :

This relies on default ℕ = 0.

@[simp]
theorem List.alternatingSum_nil {α : Type u_2} [Zero α] [Add α] [Neg α] :
[].alternatingSum = 0
@[simp]
theorem List.alternatingProd_nil {α : Type u_2} [One α] [Mul α] [Inv α] :
[].alternatingProd = 1
@[simp]
theorem List.alternatingSum_singleton {α : Type u_2} [Zero α] [Add α] [Neg α] (a : α) :
[a].alternatingSum = a
@[simp]
theorem List.alternatingProd_singleton {α : Type u_2} [One α] [Mul α] [Inv α] (a : α) :
[a].alternatingProd = a
theorem List.alternatingSum_cons_cons' {α : Type u_2} [Zero α] [Add α] [Neg α] (a : α) (b : α) (l : List α) :
(a :: b :: l).alternatingSum = a + -b + l.alternatingSum
theorem List.alternatingProd_cons_cons' {α : Type u_2} [One α] [Mul α] [Inv α] (a : α) (b : α) (l : List α) :
(a :: b :: l).alternatingProd = a * b⁻¹ * l.alternatingProd
theorem List.alternatingSum_cons_cons {α : Type u_2} [] (a : α) (b : α) (l : List α) :
(a :: b :: l).alternatingSum = a - b + l.alternatingSum
theorem List.alternatingProd_cons_cons {α : Type u_2} [] (a : α) (b : α) (l : List α) :
(a :: b :: l).alternatingProd = a / b * l.alternatingProd
abbrev List.alternatingSum_cons'.match_1 {α : Type u_1} (motive : αList αProp) :
∀ (x : α) (x_1 : List α), (∀ (a : α), motive a [])(∀ (a b : α) (l : List α), motive a (b :: l))motive x x_1
Equations
• =
Instances For
theorem List.alternatingSum_cons' {α : Type u_2} [] (a : α) (l : List α) :
(a :: l).alternatingSum = a + -l.alternatingSum
theorem List.alternatingProd_cons' {α : Type u_2} [] (a : α) (l : List α) :
(a :: l).alternatingProd = a * l.alternatingProd⁻¹
@[simp]
theorem List.alternatingSum_cons {α : Type u_2} [] (a : α) (l : List α) :
(a :: l).alternatingSum = a - l.alternatingSum
@[simp]
theorem List.alternatingProd_cons {α : Type u_2} [] (a : α) (l : List α) :
(a :: l).alternatingProd = a / l.alternatingProd
theorem List.sum_nat_mod (l : ) (n : ) :
l.sum % n = (List.map (fun (x : ) => x % n) l).sum % n
theorem List.prod_nat_mod (l : ) (n : ) :
l.prod % n = (List.map (fun (x : ) => x % n) l).prod % n
theorem List.sum_int_mod (l : ) (n : ) :
l.sum % n = (List.map (fun (x : ) => x % n) l).sum % n
theorem List.prod_int_mod (l : ) (n : ) :
l.prod % n = (List.map (fun (x : ) => x % n) l).prod % n
theorem List.sum_map_count_dedup_filter_eq_countP {α : Type u_2} [] (p : αBool) (l : List α) :
(List.map (fun (x : α) => ) (List.filter p l.dedup)).sum =

Summing the count of x over a list filtered by some p is just countP applied to p

theorem List.sum_map_count_dedup_eq_length {α : Type u_2} [] (l : List α) :
(List.map (fun (x : α) => ) l.dedup).sum = l.length
theorem map_list_sum {M : Type u_4} {N : Type u_5} [] [] {F : Type u_8} [FunLike F M N] [] (f : F) (l : List M) :
f l.sum = (List.map (f) l).sum
theorem map_list_prod {M : Type u_4} {N : Type u_5} [] [] {F : Type u_8} [FunLike F M N] [] (f : F) (l : List M) :
f l.prod = (List.map (f) l).prod
@[deprecated map_list_sum]
theorem AddMonoidHom.map_list_sum {M : Type u_4} {N : Type u_5} [] [] (f : M →+ N) (l : List M) :
f l.sum = (List.map (f) l).sum
@[deprecated map_list_prod]
theorem MonoidHom.map_list_prod {M : Type u_4} {N : Type u_5} [] [] (f : M →* N) (l : List M) :
f l.prod = (List.map (f) l).prod
@[simp]
theorem Nat.sum_eq_listSum (l : ) :
= l.sum
theorem List.length_sigma {α : Type u_2} {σ : αType u_8} (l₁ : List α) (l₂ : (a : α) → List (σ a)) :
(l₁.sigma l₂).length = (List.map (fun (a : α) => (l₂ a).length) l₁).sum
theorem List.ranges_join (l : ) :
l.ranges.join = List.range l.sum
theorem List.mem_mem_ranges_iff_lt_sum (l : ) {n : } :
(sl.ranges, n s) n < l.sum

Any entry of any member of l.ranges is strictly smaller than l.sum.

@[simp]
theorem List.length_join {α : Type u_2} (L : List (List α)) :
L.join.length = (List.map List.length L).sum
theorem List.countP_join {α : Type u_2} (p : αBool) (L : List (List α)) :
List.countP p L.join = (List.map () L).sum
theorem List.count_join {α : Type u_2} [BEq α] (L : List (List α)) (a : α) :
List.count a L.join = (List.map () L).sum
@[simp]
theorem List.length_bind {α : Type u_2} {β : Type u_3} (l : List α) (f : αList β) :
(l.bind f).length = (List.map (List.length f) l).sum
theorem List.countP_bind {α : Type u_2} {β : Type u_3} (p : βBool) (l : List α) (f : αList β) :
List.countP p (l.bind f) = (List.map ( f) l).sum
theorem List.count_bind {α : Type u_2} {β : Type u_3} [BEq β] (l : List α) (f : αList β) (x : β) :
List.count x (l.bind f) = (List.map ( f) l).sum
theorem List.take_sum_join {α : Type u_2} (L : List (List α)) (i : ) :
List.take (List.take i (List.map List.length L)).sum L.join = ().join

In a join, taking the first elements up to an index which is the sum of the lengths of the first i sublists, is the same as taking the join of the first i sublists.

theorem List.drop_sum_join {α : Type u_2} (L : List (List α)) (i : ) :
List.drop (List.take i (List.map List.length L)).sum L.join = ().join

In a join, dropping all the elements up to an index which is the sum of the lengths of the first i sublists, is the same as taking the join after dropping the first i sublists.

theorem List.drop_take_succ_join_eq_get {α : Type u_2} (L : List (List α)) (i : Fin L.length) :
List.drop (List.take (i) (List.map List.length L)).sum (List.take (List.take (i + 1) (List.map List.length L)).sum L.join) = L.get i

In a join of sublists, taking the slice between the indices A and B - 1 gives back the original sublist of index i if A is the sum of the lengths of sublists of index < i, and B is the sum of the lengths of sublists of index ≤ i.

theorem List.neg_one_mem_of_prod_eq_neg_one {l : } (h : l.prod = -1) :
-1 l

If a product of integers is -1, then at least one factor must be -1.

theorem List.length_le_sum_of_one_le (L : ) (h : iL, 1 i) :
L.length L.sum

If all elements in a list are bounded below by 1, then the length of the list is bounded by the sum of the elements.

theorem List.dvd_prod {M : Type u_4} [] {a : M} {l : List M} (ha : a l) :
a l.prod
theorem List.Sublist.prod_dvd_prod {M : Type u_4} [] {l₁ : List M} {l₂ : List M} (h : l₁.Sublist l₂) :
l₁.prod l₂.prod
abbrev List.alternatingSum_append.match_1 {α : Type u_1} (motive : List αList αProp) :
∀ (x x_1 : List α), (∀ (l₂ : List α), motive [] l₂)(∀ (a : α) (l₁ l₂ : List α), motive (a :: l₁) l₂)motive x x_1
Equations
• =
Instances For
theorem List.alternatingSum_append {α : Type u_2} [] (l₁ : List α) (l₂ : List α) :
(l₁ ++ l₂).alternatingSum = l₁.alternatingSum + (-1) ^ l₁.length l₂.alternatingSum
theorem List.alternatingProd_append {α : Type u_2} [] (l₁ : List α) (l₂ : List α) :
(l₁ ++ l₂).alternatingProd = l₁.alternatingProd * l₂.alternatingProd ^ (-1) ^ l₁.length
theorem List.alternatingSum_reverse {α : Type u_2} [] (l : List α) :
l.reverse.alternatingSum = (-1) ^ (l.length + 1) l.alternatingSum
theorem List.alternatingProd_reverse {α : Type u_2} [] (l : List α) :
l.reverse.alternatingProd = l.alternatingProd ^ (-1) ^ (l.length + 1)
theorem MulOpposite.op_list_prod {M : Type u_4} [] (l : List M) :
MulOpposite.op l.prod = (List.map MulOpposite.op l).reverse.prod
theorem MulOpposite.unop_list_prod {M : Type u_4} [] (l : ) :
l.prod.unop = (List.map MulOpposite.unop l).reverse.prod
theorem unop_map_list_prod {M : Type u_4} {N : Type u_5} [] [] {F : Type u_8} [FunLike F M Nᵐᵒᵖ] [] (f : F) (l : List M) :
(f l.prod).unop = (List.map (MulOpposite.unop f) l).reverse.prod

A morphism into the opposite monoid acts on the product by acting on the reversed elements.

@[deprecated unop_map_list_prod]
theorem MonoidHom.unop_map_list_prod {M : Type u_4} {N : Type u_5} [] [] (f : M →* Nᵐᵒᵖ) (l : List M) :
(f l.prod).unop = (List.map (MulOpposite.unop f) l).reverse.prod

A morphism into the opposite monoid acts on the product by acting on the reversed elements.