Documentation

Mathlib.Data.Finset.Piecewise

Functions defined piecewise on a finset #

This file defines Finset.piecewise: Given two functions f, g, s.piecewise f g is a function which is equal to f on s and g on the complement.

TODO #

Should we deduplicate this from Set.piecewise?

def Finset.piecewise {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] (i : ι) :
π i

s.piecewise f g is the function equal to f on the finset s, and to g on its complement.

Equations
    Instances For
      theorem Finset.piecewise_insert_self {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [DecidableEq ι] {j : ι} [(i : ι) → Decidable (i insert j s)] :
      (insert j s).piecewise f g j = f j
      @[simp]
      theorem Finset.piecewise_empty {ι : Type u_1} {π : ιSort u_2} (f g : (i : ι) → π i) [(i : ι) → Decidable (i )] :
      theorem Finset.piecewise_coe {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] [(j : ι) → Decidable (j s)] :
      (↑s).piecewise f g = s.piecewise f g
      @[simp]
      theorem Finset.piecewise_eq_of_mem {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] {i : ι} (hi : i s) :
      s.piecewise f g i = f i
      @[simp]
      theorem Finset.piecewise_eq_of_notMem {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] {i : ι} (hi : is) :
      s.piecewise f g i = g i
      @[deprecated Finset.piecewise_eq_of_notMem (since := "2025-05-23")]
      theorem Finset.piecewise_eq_of_not_mem {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] {i : ι} (hi : is) :
      s.piecewise f g i = g i

      Alias of Finset.piecewise_eq_of_notMem.

      theorem Finset.piecewise_congr {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) [(j : ι) → Decidable (j s)] {f f' g g' : (i : ι) → π i} (hf : is, f i = f' i) (hg : is, g i = g' i) :
      s.piecewise f g = s.piecewise f' g'
      @[simp]
      theorem Finset.piecewise_insert_of_ne {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] [DecidableEq ι] {i j : ι} [(i : ι) → Decidable (i insert j s)] (h : i j) :
      (insert j s).piecewise f g i = s.piecewise f g i
      theorem Finset.piecewise_insert {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] [DecidableEq ι] (j : ι) [(i : ι) → Decidable (i insert j s)] :
      (insert j s).piecewise f g = Function.update (s.piecewise f g) j (f j)
      theorem Finset.piecewise_cases {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] {i : ι} (p : π iProp) (hf : p (f i)) (hg : p (g i)) :
      p (s.piecewise f g i)
      theorem Finset.piecewise_singleton {ι : Type u_1} {π : ιSort u_2} (f g : (i : ι) → π i) [DecidableEq ι] (i : ι) :
      {i}.piecewise f g = Function.update g i (f i)
      theorem Finset.piecewise_piecewise_of_subset_left {ι : Type u_1} {π : ιSort u_2} {s t : Finset ι} [(i : ι) → Decidable (i s)] [(i : ι) → Decidable (i t)] (h : s t) (f₁ f₂ g : (a : ι) → π a) :
      s.piecewise (t.piecewise f₁ f₂) g = s.piecewise f₁ g
      @[simp]
      theorem Finset.piecewise_idem_left {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) [(j : ι) → Decidable (j s)] (f₁ f₂ g : (a : ι) → π a) :
      s.piecewise (s.piecewise f₁ f₂) g = s.piecewise f₁ g
      theorem Finset.piecewise_piecewise_of_subset_right {ι : Type u_1} {π : ιSort u_2} {s t : Finset ι} [(i : ι) → Decidable (i s)] [(i : ι) → Decidable (i t)] (h : t s) (f g₁ g₂ : (a : ι) → π a) :
      s.piecewise f (t.piecewise g₁ g₂) = s.piecewise f g₂
      @[simp]
      theorem Finset.piecewise_idem_right {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) [(j : ι) → Decidable (j s)] (f g₁ g₂ : (a : ι) → π a) :
      s.piecewise f (s.piecewise g₁ g₂) = s.piecewise f g₂
      theorem Finset.update_eq_piecewise {ι : Type u_1} {β : Type u_3} [DecidableEq ι] (f : ιβ) (i : ι) (v : β) :
      Function.update f i v = {i}.piecewise (fun (x : ι) => v) f
      theorem Finset.update_piecewise {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] [DecidableEq ι] (i : ι) (v : π i) :
      theorem Finset.update_piecewise_of_mem {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] [DecidableEq ι] {i : ι} (hi : i s) (v : π i) :
      theorem Finset.update_piecewise_of_notMem {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] [DecidableEq ι] {i : ι} (hi : is) (v : π i) :
      @[deprecated Finset.update_piecewise_of_notMem (since := "2025-05-23")]
      theorem Finset.update_piecewise_of_not_mem {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f g : (i : ι) → π i) [(j : ι) → Decidable (j s)] [DecidableEq ι] {i : ι} (hi : is) (v : π i) :

      Alias of Finset.update_piecewise_of_notMem.

      theorem Finset.piecewise_same {ι : Type u_1} {π : ιSort u_2} (s : Finset ι) (f : (i : ι) → π i) [(j : ι) → Decidable (j s)] :
      s.piecewise f f = f
      @[simp]
      theorem Finset.piecewise_univ {ι : Type u_1} {π : ιSort u_2} [Fintype ι] [(i : ι) → Decidable (i univ)] (f g : (i : ι) → π i) :
      theorem Finset.piecewise_compl {ι : Type u_1} {π : ιSort u_2} [Fintype ι] [DecidableEq ι] (s : Finset ι) [(i : ι) → Decidable (i s)] [(i : ι) → Decidable (i s)] (f g : (i : ι) → π i) :
      @[simp]
      theorem Finset.piecewise_erase_univ {ι : Type u_1} {π : ιSort u_2} [Fintype ι] [DecidableEq ι] (i : ι) (f g : (i : ι) → π i) :
      theorem Finset.piecewise_mem_set_pi {ι : Type u_1} (s : Finset ι) [(j : ι) → Decidable (j s)] {π : ιType u_3} {t : Set ι} {t' : (i : ι) → Set (π i)} {f g : (i : ι) → π i} (hf : f t.pi t') (hg : g t.pi t') :
      s.piecewise f g t.pi t'
      theorem Finset.piecewise_le_of_le_of_le {ι : Type u_1} (s : Finset ι) [(j : ι) → Decidable (j s)] {π : ιType u_3} {f g h : (i : ι) → π i} [(i : ι) → Preorder (π i)] (hf : f h) (hg : g h) :
      s.piecewise f g h
      theorem Finset.le_piecewise_of_le_of_le {ι : Type u_1} (s : Finset ι) [(j : ι) → Decidable (j s)] {π : ιType u_3} {f g h : (i : ι) → π i} [(i : ι) → Preorder (π i)] (hf : h f) (hg : h g) :
      h s.piecewise f g
      theorem Finset.piecewise_le_piecewise' {ι : Type u_1} (s : Finset ι) [(j : ι) → Decidable (j s)] {π : ιType u_3} {f g f' g' : (i : ι) → π i} [(i : ι) → Preorder (π i)] (hf : xs, f x f' x) (hg : xs, g x g' x) :
      s.piecewise f g s.piecewise f' g'
      theorem Finset.piecewise_le_piecewise {ι : Type u_1} (s : Finset ι) [(j : ι) → Decidable (j s)] {π : ιType u_3} {f g f' g' : (i : ι) → π i} [(i : ι) → Preorder (π i)] (hf : f f') (hg : g g') :
      s.piecewise f g s.piecewise f' g'
      theorem Finset.piecewise_mem_Icc_of_mem_of_mem {ι : Type u_1} (s : Finset ι) [(j : ι) → Decidable (j s)] {π : ιType u_3} {f g f' g' : (i : ι) → π i} [(i : ι) → Preorder (π i)] (hf : f Set.Icc f' g') (hg : g Set.Icc f' g') :
      s.piecewise f g Set.Icc f' g'
      theorem Finset.piecewise_mem_Icc {ι : Type u_1} (s : Finset ι) [(j : ι) → Decidable (j s)] {π : ιType u_3} {f g : (i : ι) → π i} [(i : ι) → Preorder (π i)] (h : f g) :
      theorem Finset.piecewise_mem_Icc' {ι : Type u_1} (s : Finset ι) [(j : ι) → Decidable (j s)] {π : ιType u_3} {f g : (i : ι) → π i} [(i : ι) → Preorder (π i)] (h : g f) :