Documentation

Mathlib.Data.Rel

Relations #

This file defines bundled relations. A relation between α and β is a function α → β → Prop. Relations are also known as set-valued functions, or partial multifunctions.

Main declarations #

TODO #

The Rel.comp function uses the notation r • s, rather than the more common r ∘ s for things named comp. This is because the latter is already used for function composition, and causes a clash. A better notation should be found, perhaps a variant of r ∘r s or r; s.

def Rel (α : Type u_4) (β : Type u_5) :
Type (max u_4 u_5)

A relation on α and β, aka a set-valued function, aka a partial multifunction

Equations
Instances For
    instance instCompleteLatticeRel {α : Type u_1} {β : Type u_2} :
    Equations
    • instCompleteLatticeRel = inferInstance
    instance instInhabitedRel {α : Type u_1} {β : Type u_2} :
    Inhabited (Rel α β)
    Equations
    • instInhabitedRel = inferInstance
    theorem Rel.ext {α : Type u_1} {β : Type u_2} {r s : Rel α β} :
    (∀ (a : α), r a = s a)r = s
    def Rel.inv {α : Type u_1} {β : Type u_2} (r : Rel α β) :
    Rel β α

    The inverse relation : r.inv x y ↔ r y x. Note that this is not a groupoid inverse.

    Equations
    Instances For
      theorem Rel.inv_def {α : Type u_1} {β : Type u_2} (r : Rel α β) (x : α) (y : β) :
      r.inv y x r x y
      theorem Rel.inv_inv {α : Type u_1} {β : Type u_2} (r : Rel α β) :
      r.inv.inv = r
      def Rel.dom {α : Type u_1} {β : Type u_2} (r : Rel α β) :
      Set α

      Domain of a relation

      Equations
      • r.dom = {x : α | ∃ (y : β), r x y}
      Instances For
        theorem Rel.dom_mono {α : Type u_1} {β : Type u_2} {r s : Rel α β} (h : r s) :
        r.dom s.dom
        def Rel.codom {α : Type u_1} {β : Type u_2} (r : Rel α β) :
        Set β

        Codomain aka range of a relation

        Equations
        • r.codom = {y : β | ∃ (x : α), r x y}
        Instances For
          theorem Rel.codom_inv {α : Type u_1} {β : Type u_2} (r : Rel α β) :
          r.inv.codom = r.dom
          theorem Rel.dom_inv {α : Type u_1} {β : Type u_2} (r : Rel α β) :
          r.inv.dom = r.codom
          def Rel.comp {α : Type u_1} {β : Type u_2} {γ : Type u_3} (r : Rel α β) (s : Rel β γ) :
          Rel α γ

          Composition of relation; note that it follows the CategoryTheory/ order of arguments.

          Equations
          • r.comp s x z = ∃ (y : β), r x y s y z
          Instances For
            theorem Rel.comp_assoc {α : Type u_1} {β : Type u_2} {γ : Type u_3} {δ : Type u_4} (r : Rel α β) (s : Rel β γ) (t : Rel γ δ) :
            (r.comp s).comp t = r.comp (s.comp t)
            @[simp]
            theorem Rel.comp_right_id {α : Type u_1} {β : Type u_2} (r : Rel α β) :
            r.comp Eq = r
            @[simp]
            theorem Rel.comp_left_id {α : Type u_1} {β : Type u_2} (r : Rel α β) :
            Rel.comp Eq r = r
            @[simp]
            theorem Rel.comp_right_bot {α : Type u_1} {β : Type u_2} {γ : Type u_3} (r : Rel α β) :
            r.comp =
            @[simp]
            theorem Rel.comp_left_bot {α : Type u_1} {β : Type u_2} {γ : Type u_3} (r : Rel α β) :
            .comp r =
            @[simp]
            theorem Rel.comp_right_top {α : Type u_1} {β : Type u_2} {γ : Type u_3} (r : Rel α β) :
            r.comp = fun (x : α) (x_1 : γ) => x r.dom
            @[simp]
            theorem Rel.comp_left_top {α : Type u_1} {β : Type u_2} {γ : Type u_3} (r : Rel α β) :
            .comp r = fun (x : γ) (y : β) => y r.codom
            theorem Rel.inv_id {α : Type u_1} :
            Rel.inv Eq = Eq
            theorem Rel.inv_comp {α : Type u_1} {β : Type u_2} {γ : Type u_3} (r : Rel α β) (s : Rel β γ) :
            (r.comp s).inv = s.inv.comp r.inv
            @[simp]
            theorem Rel.inv_bot {α : Type u_1} {β : Type u_2} :
            .inv =
            @[simp]
            theorem Rel.inv_top {α : Type u_1} {β : Type u_2} :
            .inv =
            def Rel.image {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set α) :
            Set β

            Image of a set under a relation

            Equations
            • r.image s = {y : β | xs, r x y}
            Instances For
              theorem Rel.mem_image {α : Type u_1} {β : Type u_2} (r : Rel α β) (y : β) (s : Set α) :
              y r.image s xs, r x y
              theorem Rel.image_subset {α : Type u_1} {β : Type u_2} (r : Rel α β) :
              ((fun (x1 x2 : Set α) => x1 x2) fun (x1 x2 : Set β) => x1 x2) r.image r.image
              theorem Rel.image_mono {α : Type u_1} {β : Type u_2} (r : Rel α β) :
              Monotone r.image
              theorem Rel.image_inter {α : Type u_1} {β : Type u_2} (r : Rel α β) (s t : Set α) :
              r.image (s t) r.image s r.image t
              theorem Rel.image_union {α : Type u_1} {β : Type u_2} (r : Rel α β) (s t : Set α) :
              r.image (s t) = r.image s r.image t
              @[simp]
              theorem Rel.image_id {α : Type u_1} (s : Set α) :
              Rel.image Eq s = s
              theorem Rel.image_comp {α : Type u_1} {β : Type u_2} {γ : Type u_3} (r : Rel α β) (s : Rel β γ) (t : Set α) :
              (r.comp s).image t = s.image (r.image t)
              theorem Rel.image_univ {α : Type u_1} {β : Type u_2} (r : Rel α β) :
              r.image Set.univ = r.codom
              @[simp]
              theorem Rel.image_empty {α : Type u_1} {β : Type u_2} (r : Rel α β) :
              r.image =
              @[simp]
              theorem Rel.image_bot {α : Type u_1} {β : Type u_2} (s : Set α) :
              .image s =
              @[simp]
              theorem Rel.image_top {α : Type u_1} {β : Type u_2} {s : Set α} (h : s.Nonempty) :
              .image s = Set.univ
              def Rel.preimage {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set β) :
              Set α

              Preimage of a set under a relation r. Same as the image of s under r.inv

              Equations
              • r.preimage s = r.inv.image s
              Instances For
                theorem Rel.mem_preimage {α : Type u_1} {β : Type u_2} (r : Rel α β) (x : α) (s : Set β) :
                x r.preimage s ys, r x y
                theorem Rel.preimage_def {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set β) :
                r.preimage s = {x : α | ys, r x y}
                theorem Rel.preimage_mono {α : Type u_1} {β : Type u_2} (r : Rel α β) {s t : Set β} (h : s t) :
                r.preimage s r.preimage t
                theorem Rel.preimage_inter {α : Type u_1} {β : Type u_2} (r : Rel α β) (s t : Set β) :
                r.preimage (s t) r.preimage s r.preimage t
                theorem Rel.preimage_union {α : Type u_1} {β : Type u_2} (r : Rel α β) (s t : Set β) :
                r.preimage (s t) = r.preimage s r.preimage t
                theorem Rel.preimage_id {α : Type u_1} (s : Set α) :
                theorem Rel.preimage_comp {α : Type u_1} {β : Type u_2} {γ : Type u_3} (r : Rel α β) (s : Rel β γ) (t : Set γ) :
                (r.comp s).preimage t = r.preimage (s.preimage t)
                theorem Rel.preimage_univ {α : Type u_1} {β : Type u_2} (r : Rel α β) :
                r.preimage Set.univ = r.dom
                @[simp]
                theorem Rel.preimage_empty {α : Type u_1} {β : Type u_2} (r : Rel α β) :
                r.preimage =
                @[simp]
                theorem Rel.preimage_inv {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set α) :
                r.inv.preimage s = r.image s
                @[simp]
                theorem Rel.preimage_bot {α : Type u_1} {β : Type u_2} (s : Set β) :
                .preimage s =
                @[simp]
                theorem Rel.preimage_top {α : Type u_1} {β : Type u_2} {s : Set β} (h : s.Nonempty) :
                .preimage s = Set.univ
                theorem Rel.image_eq_dom_of_codomain_subset {α : Type u_1} {β : Type u_2} (r : Rel α β) {s : Set β} (h : r.codom s) :
                r.preimage s = r.dom
                theorem Rel.preimage_eq_codom_of_domain_subset {α : Type u_1} {β : Type u_2} (r : Rel α β) {s : Set α} (h : r.dom s) :
                r.image s = r.codom
                theorem Rel.image_inter_dom_eq {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set α) :
                r.image (s r.dom) = r.image s
                @[simp]
                theorem Rel.preimage_inter_codom_eq {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set β) :
                r.preimage (s r.codom) = r.preimage s
                theorem Rel.inter_dom_subset_preimage_image {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set α) :
                s r.dom r.preimage (r.image s)
                theorem Rel.image_preimage_subset_inter_codom {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set β) :
                s r.codom r.image (r.preimage s)
                def Rel.core {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set β) :
                Set α

                Core of a set s : Set β w.r.t r : Rel α β is the set of x : α that are related only to elements of s. Other generalization of Function.preimage.

                Equations
                • r.core s = {x : α | ∀ (y : β), r x yy s}
                Instances For
                  theorem Rel.mem_core {α : Type u_1} {β : Type u_2} (r : Rel α β) (x : α) (s : Set β) :
                  x r.core s ∀ (y : β), r x yy s
                  theorem Rel.core_subset {α : Type u_1} {β : Type u_2} (r : Rel α β) :
                  ((fun (x1 x2 : Set β) => x1 x2) fun (x1 x2 : Set α) => x1 x2) r.core r.core
                  theorem Rel.core_mono {α : Type u_1} {β : Type u_2} (r : Rel α β) :
                  Monotone r.core
                  theorem Rel.core_inter {α : Type u_1} {β : Type u_2} (r : Rel α β) (s t : Set β) :
                  r.core (s t) = r.core s r.core t
                  theorem Rel.core_union {α : Type u_1} {β : Type u_2} (r : Rel α β) (s t : Set β) :
                  r.core s r.core t r.core (s t)
                  @[simp]
                  theorem Rel.core_univ {α : Type u_1} {β : Type u_2} (r : Rel α β) :
                  r.core Set.univ = Set.univ
                  theorem Rel.core_id {α : Type u_1} (s : Set α) :
                  Rel.core Eq s = s
                  theorem Rel.core_comp {α : Type u_1} {β : Type u_2} {γ : Type u_3} (r : Rel α β) (s : Rel β γ) (t : Set γ) :
                  (r.comp s).core t = r.core (s.core t)
                  def Rel.restrictDomain {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set α) :
                  Rel { x : α // x s } β

                  Restrict the domain of a relation to a subtype.

                  Equations
                  • r.restrictDomain s x y = r (↑x) y
                  Instances For
                    theorem Rel.image_subset_iff {α : Type u_1} {β : Type u_2} (r : Rel α β) (s : Set α) (t : Set β) :
                    r.image s t s r.core t
                    theorem Rel.image_core_gc {α : Type u_1} {β : Type u_2} (r : Rel α β) :
                    GaloisConnection r.image r.core
                    def Function.graph {α : Type u_1} {β : Type u_2} (f : αβ) :
                    Rel α β

                    The graph of a function as a relation.

                    Equations
                    Instances For
                      @[simp]
                      theorem Function.graph_def {α : Type u_1} {β : Type u_2} (f : αβ) (x : α) (y : β) :
                      Function.graph f x y f x = y
                      theorem Function.graph_injective {α : Type u_1} {β : Type u_2} :
                      Function.Injective Function.graph
                      @[simp]
                      theorem Function.graph_inj {α : Type u_1} {β : Type u_2} {f g : αβ} :
                      theorem Function.graph_id {α : Type u_1} :
                      theorem Function.graph_comp {α : Type u_1} {β : Type u_2} {γ : Type u_3} {f : βγ} {g : αβ} :
                      theorem Equiv.graph_inv {α : Type u_1} {β : Type u_2} (f : α β) :
                      Function.graph f.symm = (Function.graph f).inv
                      theorem Relation.is_graph_iff {α : Type u_1} {β : Type u_2} (r : Rel α β) :
                      (∃! f : αβ, Function.graph f = r) ∀ (x : α), ∃! y : β, r x y
                      theorem Set.image_eq {α : Type u_1} {β : Type u_2} (f : αβ) (s : Set α) :
                      f '' s = (Function.graph f).image s
                      theorem Set.preimage_eq {α : Type u_1} {β : Type u_2} (f : αβ) (s : Set β) :
                      f ⁻¹' s = (Function.graph f).preimage s
                      theorem Set.preimage_eq_core {α : Type u_1} {β : Type u_2} (f : αβ) (s : Set β) :
                      f ⁻¹' s = (Function.graph f).core s