(*  Title:      HOL/Predicate.thy

    Author:     Stefan Berghofer and Lukas Bulwahn and Florian Haftmann, TU Muenchen

*)

header {* Predicates as relations and enumerations *}

theory Predicate

imports Inductive Relation

begin

notation

  inf (infixl "\<sqinter>" 70) and

  sup (infixl "\<squnion>" 65) and

  Inf ("\<Sqinter>_" [900] 900) and

  Sup ("\<Squnion>_" [900] 900) and

  top ("\<top>") and

  bot ("\<bottom>")

subsection {* Predicates as (complete) lattices *}

subsubsection {* @{const sup} on @{typ bool} *}

lemma sup_boolI1:

  "P \<Longrightarrow> P \<squnion> Q"

  by (simp add: sup_bool_eq)

lemma sup_boolI2:

  "Q \<Longrightarrow> P \<squnion> Q"

  by (simp add: sup_bool_eq)

lemma sup_boolE:

  "P \<squnion> Q \<Longrightarrow> (P \<Longrightarrow> R) \<Longrightarrow> (Q \<Longrightarrow> R) \<Longrightarrow> R"

  by (auto simp add: sup_bool_eq)

subsubsection {* Equality and Subsets *}

lemma pred_equals_eq: "((\<lambda>x. x \<in> R) = (\<lambda>x. x \<in> S)) = (R = S)"

  by (simp add: mem_def)

lemma pred_equals_eq2 [pred_set_conv]: "((\<lambda>x y. (x, y) \<in> R) = (\<lambda>x y. (x, y) \<in> S)) = (R = S)"

  by (simp add: expand_fun_eq mem_def)

lemma pred_subset_eq: "((\<lambda>x. x \<in> R) <= (\<lambda>x. x \<in> S)) = (R <= S)"

  by (simp add: mem_def)

lemma pred_subset_eq2 [pred_set_conv]: "((\<lambda>x y. (x, y) \<in> R) <= (\<lambda>x y. (x, y) \<in> S)) = (R <= S)"

  by fast

subsubsection {* Top and bottom elements *}

lemma top1I [intro!]: "top x"

  by (simp add: top_fun_eq top_bool_eq)

lemma top2I [intro!]: "top x y"

  by (simp add: top_fun_eq top_bool_eq)

lemma bot1E [elim!]: "bot x \<Longrightarrow> P"

  by (simp add: bot_fun_eq bot_bool_eq)

lemma bot2E [elim!]: "bot x y \<Longrightarrow> P"

  by (simp add: bot_fun_eq bot_bool_eq)

subsubsection {* The empty set *}

lemma bot_empty_eq: "bot = (\<lambda>x. x \<in> {})"

  by (auto simp add: expand_fun_eq)

lemma bot_empty_eq2: "bot = (\<lambda>x y. (x, y) \<in> {})"

  by (auto simp add: expand_fun_eq)

subsubsection {* Binary union *}

lemma sup1_iff [simp]: "sup A B x \<longleftrightarrow> A x | B x"

  by (simp add: sup_fun_eq sup_bool_eq)

lemma sup2_iff [simp]: "sup A B x y \<longleftrightarrow> A x y | B x y"

  by (simp add: sup_fun_eq sup_bool_eq)

lemma sup_Un_eq [pred_set_conv]: "sup (\<lambda>x. x \<in> R) (\<lambda>x. x \<in> S) = (\<lambda>x. x \<in> R \<union> S)"

  by (simp add: expand_fun_eq)

lemma sup_Un_eq2 [pred_set_conv]: "sup (\<lambda>x y. (x, y) \<in> R) (\<lambda>x y. (x, y) \<in> S) = (\<lambda>x y. (x, y) \<in> R \<union> S)"

  by (simp add: expand_fun_eq)

lemma sup1I1 [elim?]: "A x \<Longrightarrow> sup A B x"

  by simp

lemma sup2I1 [elim?]: "A x y \<Longrightarrow> sup A B x y"

  by simp

lemma sup1I2 [elim?]: "B x \<Longrightarrow> sup A B x"

  by simp

lemma sup2I2 [elim?]: "B x y \<Longrightarrow> sup A B x y"

  by simp

text {*

  \medskip Classical introduction rule: no commitment to @{text A} vs

  @{text B}.

*}

lemma sup1CI [intro!]: "(~ B x ==> A x) ==> sup A B x"

  by auto

lemma sup2CI [intro!]: "(~ B x y ==> A x y) ==> sup A B x y"

  by auto

lemma sup1E [elim!]: "sup A B x ==> (A x ==> P) ==> (B x ==> P) ==> P"

  by simp iprover

lemma sup2E [elim!]: "sup A B x y ==> (A x y ==> P) ==> (B x y ==> P) ==> P"

  by simp iprover

subsubsection {* Binary intersection *}

lemma inf1_iff [simp]: "inf A B x \<longleftrightarrow> A x \<and> B x"

  by (simp add: inf_fun_eq inf_bool_eq)

lemma inf2_iff [simp]: "inf A B x y \<longleftrightarrow> A x y \<and> B x y"

  by (simp add: inf_fun_eq inf_bool_eq)

lemma inf_Int_eq [pred_set_conv]: "inf (\<lambda>x. x \<in> R) (\<lambda>x. x \<in> S) = (\<lambda>x. x \<in> R \<inter> S)"

  by (simp add: expand_fun_eq)

lemma inf_Int_eq2 [pred_set_conv]: "inf (\<lambda>x y. (x, y) \<in> R) (\<lambda>x y. (x, y) \<in> S) = (\<lambda>x y. (x, y) \<in> R \<inter> S)"

  by (simp add: expand_fun_eq)

lemma inf1I [intro!]: "A x ==> B x ==> inf A B x"

  by simp

lemma inf2I [intro!]: "A x y ==> B x y ==> inf A B x y"

  by simp

lemma inf1D1: "inf A B x ==> A x"

  by simp

lemma inf2D1: "inf A B x y ==> A x y"

  by simp

lemma inf1D2: "inf A B x ==> B x"

  by simp

lemma inf2D2: "inf A B x y ==> B x y"

  by simp

lemma inf1E [elim!]: "inf A B x ==> (A x ==> B x ==> P) ==> P"

  by simp

lemma inf2E [elim!]: "inf A B x y ==> (A x y ==> B x y ==> P) ==> P"

  by simp

subsubsection {* Unions of families *}

lemma SUP1_iff [simp]: "(SUP x:A. B x) b = (EX x:A. B x b)"

  by (simp add: SUPR_def Sup_fun_def Sup_bool_def) blast

lemma SUP2_iff [simp]: "(SUP x:A. B x) b c = (EX x:A. B x b c)"

  by (simp add: SUPR_def Sup_fun_def Sup_bool_def) blast

lemma SUP1_I [intro]: "a : A ==> B a b ==> (SUP x:A. B x) b"

  by auto

lemma SUP2_I [intro]: "a : A ==> B a b c ==> (SUP x:A. B x) b c"

  by auto

lemma SUP1_E [elim!]: "(SUP x:A. B x) b ==> (!!x. x : A ==> B x b ==> R) ==> R"

  by auto

lemma SUP2_E [elim!]: "(SUP x:A. B x) b c ==> (!!x. x : A ==> B x b c ==> R) ==> R"

  by auto

lemma SUP_UN_eq: "(SUP i. (\<lambda>x. x \<in> r i)) = (\<lambda>x. x \<in> (UN i. r i))"

  by (simp add: expand_fun_eq)

lemma SUP_UN_eq2: "(SUP i. (\<lambda>x y. (x, y) \<in> r i)) = (\<lambda>x y. (x, y) \<in> (UN i. r i))"

  by (simp add: expand_fun_eq)

subsubsection {* Intersections of families *}

lemma INF1_iff [simp]: "(INF x:A. B x) b = (ALL x:A. B x b)"

  by (simp add: INFI_def Inf_fun_def Inf_bool_def) blast

lemma INF2_iff [simp]: "(INF x:A. B x) b c = (ALL x:A. B x b c)"

  by (simp add: INFI_def Inf_fun_def Inf_bool_def) blast

lemma INF1_I [intro!]: "(!!x. x : A ==> B x b) ==> (INF x:A. B x) b"

  by auto

lemma INF2_I [intro!]: "(!!x. x : A ==> B x b c) ==> (INF x:A. B x) b c"

  by auto

lemma INF1_D [elim]: "(INF x:A. B x) b ==> a : A ==> B a b"

  by auto

lemma INF2_D [elim]: "(INF x:A. B x) b c ==> a : A ==> B a b c"

  by auto

lemma INF1_E [elim]: "(INF x:A. B x) b ==> (B a b ==> R) ==> (a ~: A ==> R) ==> R"

  by auto

lemma INF2_E [elim]: "(INF x:A. B x) b c ==> (B a b c ==> R) ==> (a ~: A ==> R) ==> R"

  by auto

lemma INF_INT_eq: "(INF i. (\<lambda>x. x \<in> r i)) = (\<lambda>x. x \<in> (INT i. r i))"

  by (simp add: expand_fun_eq)

lemma INF_INT_eq2: "(INF i. (\<lambda>x y. (x, y) \<in> r i)) = (\<lambda>x y. (x, y) \<in> (INT i. r i))"

  by (simp add: expand_fun_eq)

subsection {* Predicates as relations *}

subsubsection {* Composition  *}

inductive

  pred_comp  :: "['b => 'c => bool, 'a => 'b => bool] => 'a => 'c => bool"

    (infixr "OO" 75)

  for r :: "'b => 'c => bool" and s :: "'a => 'b => bool"

where

  pred_compI [intro]: "s a b ==> r b c ==> (r OO s) a c"

inductive_cases pred_compE [elim!]: "(r OO s) a c"

lemma pred_comp_rel_comp_eq [pred_set_conv]:

  "((\<lambda>x y. (x, y) \<in> r) OO (\<lambda>x y. (x, y) \<in> s)) = (\<lambda>x y. (x, y) \<in> r O s)"

  by (auto simp add: expand_fun_eq elim: pred_compE)

subsubsection {* Converse *}

inductive

  conversep :: "('a => 'b => bool) => 'b => 'a => bool"

    ("(_^--1)" [1000] 1000)

  for r :: "'a => 'b => bool"

where

  conversepI: "r a b ==> r^--1 b a"

notation (xsymbols)

  conversep  ("(_\<inverse>\<inverse>)" [1000] 1000)

lemma conversepD:

  assumes ab: "r^--1 a b"

  shows "r b a" using ab

  by cases simp

lemma conversep_iff [iff]: "r^--1 a b = r b a"

  by (iprover intro: conversepI dest: conversepD)

lemma conversep_converse_eq [pred_set_conv]:

  "(\<lambda>x y. (x, y) \<in> r)^--1 = (\<lambda>x y. (x, y) \<in> r^-1)"

  by (auto simp add: expand_fun_eq)

lemma conversep_conversep [simp]: "(r^--1)^--1 = r"

  by (iprover intro: order_antisym conversepI dest: conversepD)

lemma converse_pred_comp: "(r OO s)^--1 = s^--1 OO r^--1"

  by (iprover intro: order_antisym conversepI pred_compI

    elim: pred_compE dest: conversepD)

lemma converse_meet: "(inf r s)^--1 = inf r^--1 s^--1"

  by (simp add: inf_fun_eq inf_bool_eq)

    (iprover intro: conversepI ext dest: conversepD)

lemma converse_join: "(sup r s)^--1 = sup r^--1 s^--1"

  by (simp add: sup_fun_eq sup_bool_eq)

    (iprover intro: conversepI ext dest: conversepD)

lemma conversep_noteq [simp]: "(op ~=)^--1 = op ~="

  by (auto simp add: expand_fun_eq)

lemma conversep_eq [simp]: "(op =)^--1 = op ="

  by (auto simp add: expand_fun_eq)

subsubsection {* Domain *}

inductive

  DomainP :: "('a => 'b => bool) => 'a => bool"

  for r :: "'a => 'b => bool"

where

  DomainPI [intro]: "r a b ==> DomainP r a"

inductive_cases DomainPE [elim!]: "DomainP r a"

lemma DomainP_Domain_eq [pred_set_conv]: "DomainP (\<lambda>x y. (x, y) \<in> r) = (\<lambda>x. x \<in> Domain r)"

  by (blast intro!: Orderings.order_antisym predicate1I)

subsubsection {* Range *}

inductive

  RangeP :: "('a => 'b => bool) => 'b => bool"

  for r :: "'a => 'b => bool"

where

  RangePI [intro]: "r a b ==> RangeP r b"

inductive_cases RangePE [elim!]: "RangeP r b"

lemma RangeP_Range_eq [pred_set_conv]: "RangeP (\<lambda>x y. (x, y) \<in> r) = (\<lambda>x. x \<in> Range r)"

  by (blast intro!: Orderings.order_antisym predicate1I)

subsubsection {* Inverse image *}

definition

  inv_imagep :: "('b => 'b => bool) => ('a => 'b) => 'a => 'a => bool" where

  "inv_imagep r f == %x y. r (f x) (f y)"

lemma [pred_set_conv]: "inv_imagep (\<lambda>x y. (x, y) \<in> r) f = (\<lambda>x y. (x, y) \<in> inv_image r f)"

  by (simp add: inv_image_def inv_imagep_def)

lemma in_inv_imagep [simp]: "inv_imagep r f x y = r (f x) (f y)"

  by (simp add: inv_imagep_def)

subsubsection {* Powerset *}

definition Powp :: "('a \<Rightarrow> bool) \<Rightarrow> 'a set \<Rightarrow> bool" where

  "Powp A == \<lambda>B. \<forall>x \<in> B. A x"

lemma Powp_Pow_eq [pred_set_conv]: "Powp (\<lambda>x. x \<in> A) = (\<lambda>x. x \<in> Pow A)"

  by (auto simp add: Powp_def expand_fun_eq)

lemmas Powp_mono [mono] = Pow_mono [to_pred pred_subset_eq]

subsubsection {* Properties of relations *}

abbreviation antisymP :: "('a => 'a => bool) => bool" where

  "antisymP r == antisym {(x, y). r x y}"

abbreviation transP :: "('a => 'a => bool) => bool" where

  "transP r == trans {(x, y). r x y}"

abbreviation single_valuedP :: "('a => 'b => bool) => bool" where

  "single_valuedP r == single_valued {(x, y). r x y}"

subsection {* Predicates as enumerations *}

subsubsection {* The type of predicate enumerations (a monad) *}

datatype 'a pred = Pred "'a \<Rightarrow> bool"

primrec eval :: "'a pred \<Rightarrow> 'a \<Rightarrow> bool" where

  eval_pred: "eval (Pred f) = f"

lemma Pred_eval [simp]:

  "Pred (eval x) = x"

  by (cases x) simp

lemma eval_inject: "eval x = eval y \<longleftrightarrow> x = y"

  by (cases x) auto

definition single :: "'a \<Rightarrow> 'a pred" where

  "single x = Pred ((op =) x)"

definition bind :: "'a pred \<Rightarrow> ('a \<Rightarrow> 'b pred) \<Rightarrow> 'b pred" (infixl "\<guillemotright>=" 70) where

  "P \<guillemotright>= f = Pred (\<lambda>x. (\<exists>y. eval P y \<and> eval (f y) x))"

instantiation pred :: (type) complete_lattice

begin

definition

  "P \<le> Q \<longleftrightarrow> eval P \<le> eval Q"

definition

  "P < Q \<longleftrightarrow> eval P < eval Q"

definition

  "\<bottom> = Pred \<bottom>"

definition

  "\<top> = Pred \<top>"

definition

  "P \<sqinter> Q = Pred (eval P \<sqinter> eval Q)"

definition

  "P \<squnion> Q = Pred (eval P \<squnion> eval Q)"

definition

  "\<Sqinter>A = Pred (INFI A eval)"

definition

  "\<Squnion>A = Pred (SUPR A eval)"

instance by default

  (auto simp add: less_eq_pred_def less_pred_def

    inf_pred_def sup_pred_def bot_pred_def top_pred_def

    Inf_pred_def Sup_pred_def,

    auto simp add: le_fun_def less_fun_def le_bool_def less_bool_def

    eval_inject mem_def)

end

lemma bind_bind:

  "(P \<guillemotright>= Q) \<guillemotright>= R = P \<guillemotright>= (\<lambda>x. Q x \<guillemotright>= R)"

  by (auto simp add: bind_def expand_fun_eq)

lemma bind_single:

  "P \<guillemotright>= single = P"

  by (simp add: bind_def single_def)

lemma single_bind:

  "single x \<guillemotright>= P = P x"

  by (simp add: bind_def single_def)

lemma bottom_bind:

  "\<bottom> \<guillemotright>= P = \<bottom>"

  by (auto simp add: bot_pred_def bind_def expand_fun_eq)

lemma sup_bind:

  "(P \<squnion> Q) \<guillemotright>= R = P \<guillemotright>= R \<squnion> Q \<guillemotright>= R"

  by (auto simp add: bind_def sup_pred_def expand_fun_eq)

lemma Sup_bind: "(\<Squnion>A \<guillemotright>= f) = \<Squnion>((\<lambda>x. x \<guillemotright>= f) ` A)"

  by (auto simp add: bind_def Sup_pred_def expand_fun_eq)

lemma pred_iffI:

  assumes "\<And>x. eval A x \<Longrightarrow> eval B x"

  and "\<And>x. eval B x \<Longrightarrow> eval A x"

  shows "A = B"

proof -

  from assms have "\<And>x. eval A x \<longleftrightarrow> eval B x" by blast

  then show ?thesis by (cases A, cases B) (simp add: expand_fun_eq)

qed

lemma singleI: "eval (single x) x"

  unfolding single_def by simp

lemma singleI_unit: "eval (single ()) x"

  by simp (rule singleI)

lemma singleE: "eval (single x) y \<Longrightarrow> (y = x \<Longrightarrow> P) \<Longrightarrow> P"

  unfolding single_def by simp

lemma singleE': "eval (single x) y \<Longrightarrow> (x = y \<Longrightarrow> P) \<Longrightarrow> P"

  by (erule singleE) simp

lemma bindI: "eval P x \<Longrightarrow> eval (Q x) y \<Longrightarrow> eval (P \<guillemotright>= Q) y"

  unfolding bind_def by auto

lemma bindE: "eval (R \<guillemotright>= Q) y \<Longrightarrow> (\<And>x. eval R x \<Longrightarrow> eval (Q x) y \<Longrightarrow> P) \<Longrightarrow> P"

  unfolding bind_def by auto

lemma botE: "eval \<bottom> x \<Longrightarrow> P"

  unfolding bot_pred_def by auto

lemma supI1: "eval A x \<Longrightarrow> eval (A \<squnion> B) x"

  unfolding sup_pred_def by simp

lemma supI2: "eval B x \<Longrightarrow> eval (A \<squnion> B) x" 

  unfolding sup_pred_def by simp

lemma supE: "eval (A \<squnion> B) x \<Longrightarrow> (eval A x \<Longrightarrow> P) \<Longrightarrow> (eval B x \<Longrightarrow> P) \<Longrightarrow> P"

  unfolding sup_pred_def by auto

subsubsection {* Derived operations *}

definition if_pred :: "bool \<Rightarrow> unit pred" where

  if_pred_eq: "if_pred b = (if b then single () else \<bottom>)"

definition eq_pred :: "'a \<Rightarrow> 'a \<Rightarrow> unit pred" where

  eq_pred_eq: "eq_pred a b = if_pred (a = b)"

definition not_pred :: "unit pred \<Rightarrow> unit pred" where

  not_pred_eq: "not_pred P = (if eval P () then \<bottom> else single ())"

lemma if_predI: "P \<Longrightarrow> eval (if_pred P) ()"

  unfolding if_pred_eq by (auto intro: singleI)

lemma if_predE: "eval (if_pred b) x \<Longrightarrow> (b \<Longrightarrow> x = () \<Longrightarrow> P) \<Longrightarrow> P"

  unfolding if_pred_eq by (cases b) (auto elim: botE)

lemma eq_predI: "eval (eq_pred a a) ()"

  unfolding eq_pred_eq if_pred_eq by (auto intro: singleI)

lemma eq_predE: "eval (eq_pred a b) x \<Longrightarrow> (a = b \<Longrightarrow> x = () \<Longrightarrow> P) \<Longrightarrow> P"

  unfolding eq_pred_eq by (erule if_predE)

lemma not_predI: "\<not> P \<Longrightarrow> eval (not_pred (Pred (\<lambda>u. P))) ()"

  unfolding not_pred_eq eval_pred by (auto intro: singleI)

lemma not_predI': "\<not> eval P () \<Longrightarrow> eval (not_pred P) ()"

  unfolding not_pred_eq by (auto intro: singleI)

lemma not_predE: "eval (not_pred (Pred (\<lambda>u. P))) x \<Longrightarrow> (\<not> P \<Longrightarrow> thesis) \<Longrightarrow> thesis"

  unfolding not_pred_eq

  by (auto split: split_if_asm elim: botE)

lemma not_predE': "eval (not_pred P) x \<Longrightarrow> (\<not> eval P x \<Longrightarrow> thesis) \<Longrightarrow> thesis"

  unfolding not_pred_eq

  by (auto split: split_if_asm elim: botE)

subsubsection {* Implementation *}

datatype 'a seq = Empty | Insert "'a" "'a pred" | Join "'a pred" "'a seq"

primrec pred_of_seq :: "'a seq \<Rightarrow> 'a pred" where

    "pred_of_seq Empty = \<bottom>"

  | "pred_of_seq (Insert x P) = single x \<squnion> P"

  | "pred_of_seq (Join P xq) = P \<squnion> pred_of_seq xq"

definition Seq :: "(unit \<Rightarrow> 'a seq) \<Rightarrow> 'a pred" where

  "Seq f = pred_of_seq (f ())"

code_datatype Seq

primrec member :: "'a seq \<Rightarrow> 'a \<Rightarrow> bool"  where

  "member Empty x \<longleftrightarrow> False"

  | "member (Insert y P) x \<longleftrightarrow> x = y \<or> eval P x"

  | "member (Join P xq) x \<longleftrightarrow> eval P x \<or> member xq x"

lemma eval_member:

  "member xq = eval (pred_of_seq xq)"

proof (induct xq)

  case Empty show ?case

  by (auto simp add: expand_fun_eq elim: botE)

next

  case Insert show ?case

  by (auto simp add: expand_fun_eq elim: supE singleE intro: supI1 supI2 singleI)

next

  case Join then show ?case

  by (auto simp add: expand_fun_eq elim: supE intro: supI1 supI2)

qed

lemma eval_code [code]: "eval (Seq f) = member (f ())"

  unfolding Seq_def by (rule sym, rule eval_member)

lemma single_code [code]:

  "single x = Seq (\<lambda>u. Insert x \<bottom>)"

  unfolding Seq_def by simp

primrec "apply" :: "('a \<Rightarrow> 'b Predicate.pred) \<Rightarrow> 'a seq \<Rightarrow> 'b seq" where

    "apply f Empty = Empty"

  | "apply f (Insert x P) = Join (f x) (Join (P \<guillemotright>= f) Empty)"

  | "apply f (Join P xq) = Join (P \<guillemotright>= f) (apply f xq)"

lemma apply_bind:

  "pred_of_seq (apply f xq) = pred_of_seq xq \<guillemotright>= f"

proof (induct xq)

  case Empty show ?case

    by (simp add: bottom_bind)

next

  case Insert show ?case

    by (simp add: single_bind sup_bind)

next

  case Join then show ?case

    by (simp add: sup_bind)

qed

lemma bind_code [code]:

  "Seq g \<guillemotright>= f = Seq (\<lambda>u. apply f (g ()))"

  unfolding Seq_def by (rule sym, rule apply_bind)

lemma bot_set_code [code]:

  "\<bottom> = Seq (\<lambda>u. Empty)"

  unfolding Seq_def by simp

lemma sup_code [code]:

  "Seq f \<squnion> Seq g = Seq (\<lambda>u. case f ()

    of Empty \<Rightarrow> g ()

     | Insert x P \<Rightarrow> Insert x (P \<squnion> Seq g)

     | Join P xq \<Rightarrow> Join (Seq g) (Join P xq))" (*FIXME order!?*)

proof (cases "f ()")

  case Empty

  thus ?thesis

    unfolding Seq_def by (simp add: sup_commute [of "\<bottom>"] sup_bot)

next

  case Insert

  thus ?thesis

    unfolding Seq_def by (simp add: sup_assoc)

next

  case Join

  thus ?thesis

    unfolding Seq_def by (simp add: sup_commute [of "pred_of_seq (g ())"] sup_assoc)

qed

declare eq_pred_def [code, code del]

no_notation

  inf (infixl "\<sqinter>" 70) and

  sup (infixl "\<squnion>" 65) and

  Inf ("\<Sqinter>_" [900] 900) and

  Sup ("\<Squnion>_" [900] 900) and

  top ("\<top>") and

  bot ("\<bottom>") and

  bind (infixl "\<guillemotright>=" 70)

hide (open) type pred seq

hide (open) const Pred eval single bind if_pred eq_pred not_pred

  Empty Insert Join Seq member "apply"

end