(*  Title:      HOL/List.thy

     ID:         $Id$

     Author:     Tobias Nipkow

     Copyright   1994 TU Muenchen

 The datatype of finite lists.

 *)

 List = Datatype + WF_Rel +

 datatype 'a list = "[]" ("[]") | "#" 'a ('a list) (infixr 65)

 consts

   "@"         :: ['a list, 'a list] => 'a list            (infixr 65)

   filter      :: ['a => bool, 'a list] => 'a list

   concat      :: 'a list list => 'a list

   foldl       :: [['b,'a] => 'b, 'b, 'a list] => 'b

   hd, last    :: 'a list => 'a

   set         :: 'a list => 'a set

   list_all    :: ('a => bool) => ('a list => bool)

   map         :: ('a=>'b) => ('a list => 'b list)

   mem         :: ['a, 'a list] => bool                    (infixl 55)

   nth         :: ['a list, nat] => 'a			  (infixl "!" 100)

   list_update :: 'a list => nat => 'a => 'a list

   take, drop  :: [nat, 'a list] => 'a list

   takeWhile,

   dropWhile   :: ('a => bool) => 'a list => 'a list

   tl, butlast :: 'a list => 'a list

   rev         :: 'a list => 'a list

   zip	      :: "'a list => 'b list => ('a * 'b) list"

   upt         :: nat => nat => nat list                   ("(1[_../_'(])")

   remdups     :: 'a list => 'a list

   nodups      :: "'a list => bool"

   replicate   :: nat => 'a => 'a list

 nonterminals

   lupdbinds  lupdbind

 syntax

   (* list Enumeration *)

   "@list"     :: args => 'a list                          ("[(_)]")

   (* Special syntax for filter *)

   "@filter"   :: [pttrn, 'a list, bool] => 'a list        ("(1[_:_ ./ _])")

   (* list update *)

   "_lupdbind"      :: ['a, 'a] => lupdbind            ("(2_ :=/ _)")

   ""               :: lupdbind => lupdbinds           ("_")

   "_lupdbinds"     :: [lupdbind, lupdbinds] => lupdbinds ("_,/ _")

   "_LUpdate"       :: ['a, lupdbinds] => 'a           ("_/[(_)]" [900,0] 900)

   upto        :: nat => nat => nat list                   ("(1[_../_])")

 translations

   "[x, xs]"     == "x#[xs]"

   "[x]"         == "x#[]"

   "[x:xs . P]"  == "filter (%x. P) xs"

   "_LUpdate xs (_lupdbinds b bs)"  == "_LUpdate (_LUpdate xs b) bs"

   "xs[i:=x]"                       == "list_update xs i x"

   "[i..j]" == "[i..(Suc j)(]"

 syntax (symbols)

   "@filter"   :: [pttrn, 'a list, bool] => 'a list        ("(1[_\\<in>_ ./ _])")

 consts

   lists        :: 'a set => 'a list set

   inductive "lists A"

   intrs

     Nil  "[]: lists A"

     Cons "[| a: A;  l: lists A |] ==> a#l : lists A"

 (*Function "size" is overloaded for all datatypes.  Users may refer to the

   list version as "length".*)

 syntax   length :: 'a list => nat

 translations  "length"  =>  "size:: _ list => nat"

 primrec

   "hd([]) = arbitrary"

   "hd(x#xs) = x"

 primrec

   "tl([]) = []"

   "tl(x#xs) = xs"

 primrec

   "last [] = arbitrary"

   "last(x#xs) = (if xs=[] then x else last xs)"

 primrec

   "butlast [] = []"

   "butlast(x#xs) = (if xs=[] then [] else x#butlast xs)"

 primrec

   "x mem [] = False"

   "x mem (y#ys) = (if y=x then True else x mem ys)"

 primrec

   "set [] = {}"

   "set (x#xs) = insert x (set xs)"

 primrec

   list_all_Nil  "list_all P [] = True"

   list_all_Cons "list_all P (x#xs) = (P(x) & list_all P xs)"

 primrec

   "map f [] = []"

   "map f (x#xs) = f(x)#map f xs"

 primrec

   append_Nil  "[]    @ys = ys"

   append_Cons "(x#xs)@ys = x#(xs@ys)"

 primrec

   "rev([]) = []"

   "rev(x#xs) = rev(xs) @ [x]"

 primrec

   "filter P [] = []"

   "filter P (x#xs) = (if P x then x#filter P xs else filter P xs)"

 primrec

   "foldl f a [] = a"

   "foldl f a (x#xs) = foldl f (f a x) xs"

 primrec

   "concat([]) = []"

   "concat(x#xs) = x @ concat(xs)"

 primrec

   drop_Nil  "drop n [] = []"

   drop_Cons "drop n (x#xs) = (case n of 0 => x#xs | Suc(m) => drop m xs)"

 primrec

   take_Nil  "take n [] = []"

   take_Cons "take n (x#xs) = (case n of 0 => [] | Suc(m) => x # take m xs)"

 primrec

   "xs!0 = hd xs"

   "xs!(Suc n) = (tl xs)!n"

 primrec

  "    [][i:=v] = []"

  "(x#xs)[i:=v] = (case i of 0     => v # xs 

 			  | Suc j => x # xs[j:=v])"

 primrec

   "takeWhile P [] = []"

   "takeWhile P (x#xs) = (if P x then x#takeWhile P xs else [])"

 primrec

   "dropWhile P [] = []"

   "dropWhile P (x#xs) = (if P x then dropWhile P xs else x#xs)"

 primrec

   "zip xs []     = []"

   "zip xs (y#ys) = (hd xs,y)#zip (tl xs) ys"

 primrec

   "[i..0(] = []"

   "[i..(Suc j)(] = (if i <= j then [i..j(] @ [j] else [])"

 primrec

   "nodups []     = True"

   "nodups (x#xs) = (x ~: set xs & nodups xs)"

 primrec

   "remdups [] = []"

   "remdups (x#xs) = (if x : set xs then remdups xs else x # remdups xs)"

 primrec

   replicate_0   "replicate 0 x       = []"

   replicate_Suc "replicate (Suc n) x = x # replicate n x"

 (** Lexcicographic orderings on lists **)

 consts

  lexn :: "('a * 'a)set => nat => ('a list * 'a list)set"

 primrec

 "lexn r 0       = {}"

 "lexn r (Suc n) = (prod_fun (split op#) (split op#) `` (r ** lexn r n)) Int

                   {(xs,ys). length xs = Suc n & length ys = Suc n}"

 constdefs

  lex :: "('a * 'a)set => ('a list * 'a list)set"

 "lex r == UN n. lexn r n"

  lexico :: "('a * 'a)set => ('a list * 'a list)set"

 "lexico r == inv_image (less_than ** lex r) (%xs. (length xs, xs))"

 end

 ML

 local

 (* translating size::list -> length *)

 fun size_tr' _ (Type ("fun", (Type ("list", _) :: _))) [t] =

       Syntax.const "length" $ t

   | size_tr' _ _ _ = raise Match;

 in

 val typed_print_translation = [("size", size_tr')];

 end;