Documentation

Init.Internal.Order.Basic

This module contains some basic definitions and results from domain theory, intended to be used as the underlying construction of the partial_fixpoint feature. It is not meant to be used as a general purpose library for domain theory, but can be of interest to users who want to extend the partial_fixpoint machinery (e.g. mark more functions as monotone or register more monads).

This follows the corresponding Isabelle development, as also described in Alexander Krauss: Recursive Definitions of Monadic Functions.

class Lean.Order.PartialOrder (α : Sort u) :
Sort (max 1 u)

A partial order is a reflexive, transitive and antisymmetric relation.

This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

  • rel : α → α → Prop

    A “less-or-equal-to” or “approximates” relation.

    This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

  • rel_refl {x : α} : rel x x

    The “less-or-equal-to” or “approximates” relation is reflexive.

  • rel_trans {x y z : α} : rel x y → rel y z → rel x z

    The “less-or-equal-to” or “approximates” relation is transitive.

  • rel_antisymm {x y : α} : rel x y → rel y x → x = y

    The “less-or-equal-to” or “approximates” relation is antisymmetric.

Instances

    A “less-or-equal-to” or “approximates” relation.

    This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

    Equations
    Instances For
      theorem Lean.Order.PartialOrder.rel_of_eq {α : Sort u} [PartialOrder α] {x y : α} (h : x = y) :
      rel x y
      def Lean.Order.chain {α : Sort u} [PartialOrder α] (c : α → Prop) :

      A chain is a totally ordered set (representing a set as a predicate).

      This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

      Equations
      Instances For
        class Lean.Order.CCPO (α : Sort u) extends Lean.Order.PartialOrder α :
        Sort (max 1 u)

        A chain-complete partial order (CCPO) is a partial order where every chain has a least upper bound.

        This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

        • rel : α → α → Prop
        • rel_refl {x : α} : rel x x
        • rel_trans {x y z : α} : rel x y → rel y z → rel x z
        • rel_antisymm {x y : α} : rel x y → rel y x → x = y
        • csup : (α → Prop) → α

          The least upper bound of a chain.

          This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

        • csup_spec {x : α} {c : α → Prop} (hc : chain c) : PartialOrder.rel (csup c) x ↔ ∀ (y : α), c y → PartialOrder.rel y x

          csup c is the least upper bound of the chain c when all elements x that are at least as large as csup c are at least as large as all elements of c, and vice versa.

        Instances
          theorem Lean.Order.csup_le {α : Sort u} [CCPO α] {x : α} {c : α → Prop} (hchain : chain c) :
          (∀ (y : α), c y → PartialOrder.rel y x) → PartialOrder.rel (CCPO.csup c) x
          theorem Lean.Order.le_csup {α : Sort u} [CCPO α] {c : α → Prop} (hchain : chain c) {y : α} (hy : c y) :
          def Lean.Order.bot {α : Sort u} [CCPO α] :
          α

          The bottom element is the least upper bound of the empty chain.

          This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

          Equations
          Instances For
            theorem Lean.Order.bot_le {α : Sort u} [CCPO α] (x : α) :
            class Lean.Order.CompleteLattice (α : Sort u) extends Lean.Order.PartialOrder α :
            Sort (max 1 u)

            A complete lattice is a partial order where every subset has a least upper bound.

            Instances
              theorem Lean.Order.sup_le {α : Sort u} [CompleteLattice α] {x : α} {c : α → Prop} :
              (∀ (y : α), c y → PartialOrder.rel y x) → PartialOrder.rel (CompleteLattice.sup c) x
              theorem Lean.Order.le_sup {α : Sort u} [CompleteLattice α] {c : α → Prop} {y : α} (hy : c y) :
              def Lean.Order.inf {α : Sort u} [CompleteLattice α] (c : α → Prop) :
              α
              Equations
              Instances For
                theorem Lean.Order.inf_spec {α : Sort u} [CompleteLattice α] {x : α} {c : α → Prop} :
                PartialOrder.rel x (inf c) ↔ ∀ (y : α), c y → PartialOrder.rel x y
                theorem Lean.Order.le_inf {α : Sort u} [CompleteLattice α] {x : α} {c : α → Prop} :
                (∀ (y : α), c y → PartialOrder.rel x y) → PartialOrder.rel x (inf c)
                theorem Lean.Order.inf_le {α : Sort u} [CompleteLattice α] {c : α → Prop} {y : α} (hy : c y) :
                def Lean.Order.monotone {α : Sort u} [PartialOrder α] {β : Sort v} [PartialOrder β] (f : α → β) :

                A function is monotone if it maps related elements to related elements.

                This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

                Equations
                Instances For
                  theorem Lean.Order.monotone_const {α : Sort u} [PartialOrder α] {β : Sort v} [PartialOrder β] (c : β) :
                  monotone fun (x : α) => c
                  theorem Lean.Order.monotone_id {α : Sort u} [PartialOrder α] :
                  monotone fun (x : α) => x
                  theorem Lean.Order.monotone_compose {α : Sort u} [PartialOrder α] {β : Sort v} [PartialOrder β] {γ : Sort w} [PartialOrder γ] {f : α → β} {g : β → γ} (hf : monotone f) (hg : monotone g) :
                  monotone fun (x : α) => g (f x)
                  def Lean.Order.admissible {α : Sort u} [CCPO α] (P : α → Prop) :

                  A predicate is admissible if it can be transferred from the elements of a chain to the chains least upper bound. Such predicates can be used in fixpoint induction.

                  This definition implies P ⊥. Sometimes (e.g. in Isabelle) the empty chain is excluded from this definition, and P ⊥ is a separate condition of the induction predicate.

                  This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

                  Equations
                  Instances For
                    theorem Lean.Order.admissible_const_true {α : Sort u} [CCPO α] :
                    admissible fun (x : α) => True
                    theorem Lean.Order.admissible_and {α : Sort u} [CCPO α] (P Q : α → Prop) (hadm₁ : admissible P) (hadm₂ : admissible Q) :
                    admissible fun (x : α) => P x ∧ Q x
                    theorem Lean.Order.chain_conj {α : Sort u} [CCPO α] (c P : α → Prop) (hchain : chain c) :
                    chain fun (x : α) => c x ∧ P x
                    theorem Lean.Order.csup_conj {α : Sort u} [CCPO α] (c P : α → Prop) (hchain : chain c) (h : ∀ (x : α), c x → ∃ (y : α), c y ∧ PartialOrder.rel x y ∧ P y) :
                    CCPO.csup c = CCPO.csup fun (x : α) => c x ∧ P x
                    theorem Lean.Order.admissible_or {α : Sort u} [CCPO α] (P Q : α → Prop) (hadm₁ : admissible P) (hadm₂ : admissible Q) :
                    admissible fun (x : α) => P x ∨ Q x
                    def Lean.Order.admissible_pi {α : Sort u} [CCPO α] {β : Sort u_1} (P : α → β → Prop) (hadm₁ : ∀ (y : β), admissible fun (x : α) => P x y) :
                    admissible fun (x : α) => ∀ (y : β), P x y
                    Equations
                    • ⋯ = ⋯
                    Instances For
                      def Lean.Order.lfp {α : Sort u} [CompleteLattice α] (f : α → α) :
                      α
                      Equations
                      Instances For
                        def Lean.Order.lfp_monotone {α : Sort u} [CompleteLattice α] (f : α → α) (hm : monotone f) :
                        α
                        Equations
                        Instances For
                          theorem Lean.Order.lfp_prefixed {α : Sort u} [CompleteLattice α] {f : α → α} {hm : monotone f} :
                          theorem Lean.Order.lfp_postfixed {α : Sort u} [CompleteLattice α] {f : α → α} {hm : monotone f} :
                          theorem Lean.Order.lfp_fix {α : Sort u} [CompleteLattice α] {f : α → α} (hm : monotone f) :
                          lfp f = f (lfp f)
                          theorem Lean.Order.lfp_monotone_fix {α : Sort u} [CompleteLattice α] {f : α → α} {hm : monotone f} :
                          theorem Lean.Order.lfp_le_of_le {α : Sort u} [CompleteLattice α] {x : α} {f : α → α} :

                          Park induction principle for least fixpoint. In general, this construction does not require monotonicity of f. Monotonicity is required to show that lfp f is indeed a fixpoint of f.

                          theorem Lean.Order.lfp_le_of_le_monotone {α : Sort u} [CompleteLattice α] (f : α → α) {hm : monotone f} (x : α) :

                          Park induction for least fixpoint of a monotone function f. Takes an explicit witness of f being monotone.

                          inductive Lean.Order.iterates {α : Sort u} [CCPO α] (f : α → α) :
                          α → Prop

                          The transfinite iteration of a function f is a set that is ⊥ and is closed under application of f and csup.

                          This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

                          Instances For
                            theorem Lean.Order.chain_iterates {α : Sort u} [CCPO α] {f : α → α} (hf : monotone f) :
                            theorem Lean.Order.rel_f_of_iterates {α : Sort u} [CCPO α] {f : α → α} (hf : monotone f) {x : α} (hx : iterates f x) :
                            def Lean.Order.fix {α : Sort u} [CCPO α] (f : α → α) (hmono : monotone f) :
                            α

                            The least fixpoint of a monotone function is the least upper bound of its transfinite iteration.

                            The monotone f assumption is not strictly necessarily for the definition, but without this the definition is not very meaningful and it simplifies applying theorems like fix_eq if every use of fix already has the monotonicity requirement.

                            This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

                            Equations
                            Instances For
                              theorem Lean.Order.fix_eq {α : Sort u} [CCPO α] {f : α → α} (hf : monotone f) :
                              fix f hf = f (fix f hf)

                              The main fixpoint theorem for fixed points of monotone functions in chain-complete partial orders.

                              This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

                              theorem Lean.Order.fix_induct {α : Sort u} [CCPO α] {f : α → α} (hf : monotone f) (motive : α → Prop) (hadm : admissible motive) (h : ∀ (x : α), motive x → motive (f x)) :
                              motive (fix f hf)

                              The fixpoint induction theme: An admissible predicate holds for a least fixpoint if it is preserved by the fixpoint's function.

                              This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

                              instance Lean.Order.instOrderPi {α : Sort u} {β : α → Sort v} [(x : α) → PartialOrder (β x)] :
                              PartialOrder ((x : α) → β x)
                              Equations
                              theorem Lean.Order.monotone_of_monotone_apply {α : Sort u} {β : α → Sort v} {γ : Sort w} [PartialOrder γ] [(x : α) → PartialOrder (β x)] (f : γ → (x : α) → β x) (h : ∀ (y : α), monotone fun (x : γ) => f x y) :
                              theorem Lean.Order.monotone_apply {α : Sort u} {β : α → Sort v} {γ : Sort w} [PartialOrder γ] [(x : α) → PartialOrder (β x)] (a : α) (f : γ → (x : α) → β x) (h : monotone f) :
                              monotone fun (x : γ) => f x a
                              theorem Lean.Order.chain_apply {α : Sort u} {β : α → Sort v} [(x : α) → PartialOrder (β x)] {c : ((x : α) → β x) → Prop} (hc : chain c) (x : α) :
                              chain fun (y : β x) => ∃ (f : (x : α) → β x), c f ∧ f x = y
                              def Lean.Order.fun_csup {α : Sort u} {β : α → Sort v} [(x : α) → CCPO (β x)] (c : ((x : α) → β x) → Prop) (x : α) :
                              β x
                              Equations
                              Instances For
                                def Lean.Order.fun_sup {α : Sort u} {β : α → Sort v} [(x : α) → CompleteLattice (β x)] (c : ((x : α) → β x) → Prop) (x : α) :
                                β x
                                Equations
                                Instances For
                                  instance Lean.Order.instCCPOPi {α : Sort u} {β : α → Sort v} [(x : α) → CCPO (β x)] :
                                  CCPO ((x : α) → β x)
                                  Equations
                                  instance Lean.Order.instCompleteLatticePi {α : Sort u} {β : α → Sort v} [(x : α) → CompleteLattice (β x)] :
                                  CompleteLattice ((x : α) → β x)
                                  Equations
                                  def Lean.Order.admissible_apply {α : Sort u} {β : α → Sort v} [(x : α) → CCPO (β x)] (P : (x : α) → β x → Prop) (x : α) (hadm : admissible (P x)) :
                                  admissible fun (f : (x : α) → β x) => P x (f x)
                                  Equations
                                  • ⋯ = ⋯
                                  Instances For
                                    def Lean.Order.admissible_pi_apply {α : Sort u} {β : α → Sort v} [(x : α) → CCPO (β x)] (P : (x : α) → β x → Prop) (hadm : ∀ (x : α), admissible (P x)) :
                                    admissible fun (f : (x : α) → β x) => ∀ (x : α), P x (f x)
                                    Equations
                                    • ⋯ = ⋯
                                    Instances For
                                      theorem Lean.Order.monotone_ite {α : Sort u} {β : Sort v} [PartialOrder α] [PartialOrder β] (c : Prop) [Decidable c] (k₁ k₂ : α → β) (hmono₁ : monotone k₁) (hmono₂ : monotone k₂) :
                                      monotone fun (x : α) => if c then k₁ x else k₂ x
                                      theorem Lean.Order.monotone_dite {α : Sort u} {β : Sort v} [PartialOrder α] [PartialOrder β] (c : Prop) [Decidable c] (k₁ : α → c → β) (k₂ : α → ¬c → β) (hmono₁ : monotone k₁) (hmono₂ : monotone k₂) :
                                      monotone fun (x : α) => dite c (k₁ x) (k₂ x)
                                      Equations
                                      • One or more equations did not get rendered due to their size.
                                      theorem Lean.Order.PProd.monotone_mk {α : Sort u} {β : Sort v} {γ : Sort w} [PartialOrder α] [PartialOrder β] [PartialOrder γ] {f : γ → α} {g : γ → β} (hf : monotone f) (hg : monotone g) :
                                      monotone fun (x : γ) => ⟨f x, g x⟩
                                      theorem Lean.Order.PProd.monotone_fst {α : Sort u} {β : Sort v} {γ : Sort w} [PartialOrder α] [PartialOrder β] [PartialOrder γ] {f : γ → α ×' β} (hf : monotone f) :
                                      monotone fun (x : γ) => (f x).fst
                                      theorem Lean.Order.PProd.monotone_snd {α : Sort u} {β : Sort v} {γ : Sort w} [PartialOrder α] [PartialOrder β] [PartialOrder γ] {f : γ → α ×' β} (hf : monotone f) :
                                      monotone fun (x : γ) => (f x).snd
                                      def Lean.Order.PProd.chain.fst {α : Sort u} {β : Sort v} [CCPO α] [CCPO β] (c : α ×' β → Prop) :
                                      α → Prop
                                      Equations
                                      Instances For
                                        def Lean.Order.PProd.chain.snd {α : Sort u} {β : Sort v} [CCPO α] [CCPO β] (c : α ×' β → Prop) :
                                        β → Prop
                                        Equations
                                        Instances For
                                          def Lean.Order.PProd.fst {α : Sort u} {β : Sort v} [CompleteLattice α] [CompleteLattice β] (c : α ×' β → Prop) :
                                          α → Prop
                                          Equations
                                          Instances For
                                            def Lean.Order.PProd.snd {α : Sort u} {β : Sort v} [CompleteLattice α] [CompleteLattice β] (c : α ×' β → Prop) :
                                            β → Prop
                                            Equations
                                            Instances For
                                              theorem Lean.Order.PProd.chain.chain_fst {α : Sort u} {β : Sort v} [CCPO α] [CCPO β] {c : α ×' β → Prop} (hchain : chain c) :
                                              theorem Lean.Order.PProd.chain.chain_snd {α : Sort u} {β : Sort v} [CCPO α] [CCPO β] {c : α ×' β → Prop} (hchain : chain c) :
                                              Equations
                                              • One or more equations did not get rendered due to their size.
                                              instance Lean.Order.instCCPOPProd {α : Sort u} {β : Sort v} [CCPO α] [CCPO β] :
                                              CCPO (α ×' β)
                                              Equations
                                              • One or more equations did not get rendered due to their size.
                                              theorem Lean.Order.admissible_pprod_fst {α : Sort u} {β : Sort v} [CCPO α] [CCPO β] (P : α → Prop) (hadm : admissible P) :
                                              admissible fun (x : α ×' β) => P x.fst
                                              theorem Lean.Order.admissible_pprod_snd {α : Sort u} {β : Sort v} [CCPO α] [CCPO β] (P : β → Prop) (hadm : admissible P) :
                                              admissible fun (x : α ×' β) => P x.snd
                                              def Lean.Order.FlatOrder {α : Sort u} (b : α) :

                                              FlatOrder b wraps the type α with the flat partial order generated by ∀ x, b ⊑ x.

                                              This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

                                              Equations
                                              Instances For
                                                inductive Lean.Order.FlatOrder.rel {α : Sort u} {b : α} (x y : FlatOrder b) :

                                                The flat partial order generated by ∀ x, b ⊑ x.

                                                This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

                                                Instances For
                                                  Equations
                                                  noncomputable def Lean.Order.flat_csup {α : Sort u} {b : α} (c : FlatOrder b → Prop) :
                                                  Equations
                                                  Instances For
                                                    noncomputable instance Lean.Order.FlatOrder.instCCPO {α : Sort u} {b : α} :
                                                    Equations
                                                    theorem Lean.Order.admissible_flatOrder {α : Sort u} {b : α} (P : FlatOrder b → Prop) (hnot : P b) :
                                                    class Lean.Order.MonoBind (m : Type u → Type v) [Bind m] [(α : Type u) → PartialOrder (m α)] :

                                                    The class MonoBind m indicates that every m α has a PartialOrder, and that the bind operation on m is monotone in both arguments with regard to that order.

                                                    This is intended to be used in the construction of partial_fixpoint, and not meant to be used otherwise.

                                                    Instances
                                                      theorem Lean.Order.monotone_bind (m : Type u → Type v) [Bind m] [(α : Type u) → PartialOrder (m α)] [MonoBind m] {α β : Type u} {γ : Type w} [PartialOrder γ] (f : γ → m α) (g : γ → α → m β) (hmono₁ : monotone f) (hmono₂ : monotone g) :
                                                      monotone fun (x : γ) => f x >>= g x
                                                      theorem Lean.Order.Option.admissible_eq_some {α : Type u_1} (P : Prop) (y : α) :
                                                      admissible fun (x : Option α) => x = some y → P
                                                      instance Lean.Order.instPartialOrderExceptTOfMonad {m : Type u_1 → Type u_2} {ε α : Type u_1} [Monad m] [inst : (α : Type u_1) → PartialOrder (m α)] :
                                                      Equations
                                                      instance Lean.Order.instCCPOExceptTOfMonadOfPartialOrder {m : Type u_1 → Type u_2} {ε α : Type u_1} [Monad m] [(α : Type u_1) → PartialOrder (m α)] [inst : (α : Type u_1) → CCPO (m α)] :
                                                      CCPO (ExceptT ε m α)
                                                      Equations
                                                      instance Lean.Order.instMonoBindExceptTOfCCPO {m : Type u_1 → Type u_2} {ε : Type u_1} [Monad m] [(α : Type u_1) → PartialOrder (m α)] [(α : Type u_1) → CCPO (m α)] [MonoBind m] :
                                                      Equations
                                                      • One or more equations did not get rendered due to their size.
                                                      Equations
                                                      • One or more equations did not get rendered due to their size.
                                                      theorem Lean.Order.implication_order_monotone_exists {α : Sort u_1} [PartialOrder α] {β : Sort u_2} (f : α → β → ImplicationOrder) (h : monotone f) :
                                                      monotone fun (x : α) => Exists (f x)
                                                      theorem Lean.Order.implication_order_monotone_forall {α : Sort u_1} [PartialOrder α] {β : Sort u_2} (f : α → β → ImplicationOrder) (h : monotone f) :
                                                      monotone fun (x : α) => ∀ (y : β), f x y
                                                      theorem Lean.Order.implication_order_monotone_and {α : Sort u_1} [PartialOrder α] (f₁ f₂ : α → ImplicationOrder) (h₁ : monotone f₁) (h₂ : monotone f₂) :
                                                      monotone fun (x : α) => f₁ x ∧ f₂ x
                                                      theorem Lean.Order.implication_order_monotone_or {α : Sort u_1} [PartialOrder α] (f₁ f₂ : α → ImplicationOrder) (h₁ : monotone f₁) (h₂ : monotone f₂) :
                                                      monotone fun (x : α) => f₁ x ∨ f₂ x
                                                      Equations
                                                      • One or more equations did not get rendered due to their size.
                                                      Equations
                                                      • One or more equations did not get rendered due to their size.
                                                      theorem Lean.Order.coind_monotone_exists {α : Sort u_1} [PartialOrder α] {β : Sort u_2} (f : α → β → ReverseImplicationOrder) (h : monotone f) :
                                                      monotone fun (x : α) => Exists (f x)
                                                      theorem Lean.Order.coind_monotone_forall {α : Sort u_1} [PartialOrder α] {β : Sort u_2} (f : α → β → ReverseImplicationOrder) (h : monotone f) :
                                                      monotone fun (x : α) => ∀ (y : β), f x y
                                                      theorem Lean.Order.coind_monotone_and {α : Sort u_1} [PartialOrder α] (f₁ f₂ : α → Prop) (h₁ : monotone f₁) (h₂ : monotone f₂) :
                                                      monotone fun (x : α) => f₁ x ∧ f₂ x
                                                      theorem Lean.Order.coind_monotone_or {α : Sort u_1} [PartialOrder α] (f₁ f₂ : α → Prop) (h₁ : monotone f₁) (h₂ : monotone f₂) :
                                                      monotone fun (x : α) => f₁ x ∨ f₂ x
                                                      theorem Lean.Order.coind_not {α : Sort u_1} [PartialOrder α] (f₁ : α → Prop) (h₁ : monotone f₁) :
                                                      monotone fun (x : α) => ¬f₁ x
                                                      theorem Lean.Order.ind_not {α : Sort u_1} [PartialOrder α] (f₁ : α → Prop) (h₁ : monotone f₁) :
                                                      monotone fun (x : α) => ¬f₁ x
                                                      theorem Lean.Order.ind_impl {α : Sort u_1} [PartialOrder α] (f₁ f₂ : α → Prop) (h₁ : monotone f₁) (h₂ : monotone f₂) :
                                                      monotone fun (x : α) => f₁ x → f₂ x
                                                      theorem Lean.Order.coind_impl {α : Sort u_1} [PartialOrder α] (f₁ f₂ : α → Prop) (h₁ : monotone f₁) (h₂ : monotone f₂) :
                                                      monotone fun (x : α) => f₁ x → f₂ x
                                                      def Lean.Order.Example.findF (P : Nat → Bool) (rec : Nat → Option Nat) (x : Nat) :
                                                      Equations
                                                      Instances For
                                                        theorem Lean.Order.Example.find_spec {P : Nat → Bool} (n m : Nat) :
                                                        find P n = some m → n ≤ m ∧ P m = true