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Linux 2.6 - man page for lists (linux section 3erl)

lists(3erl)			     Erlang Module Definition			      lists(3erl)

NAME
       lists - List Processing Functions

DESCRIPTION
       This module contains functions for list processing.

       Unless  otherwise  stated,  all functions assume that position numbering starts at 1. That
       is, the first element of a list is at position 1.

       Two terms T1 and T2 compare equal if T1 == T2 evaluates to true . They match if T1 =:=  T2
       evaluates to true .

       Whenever  an ordering function F is expected as argument, it is assumed that the following
       properties hold of F for all x, y and z:

	 * if x F y and y F x then x = y ( F is antisymmetric);

	 * if x F y and y F z then x F z ( F is transitive);

	 * x F y or y F x ( F is total).

       An example of a typical ordering function is less than or equal to, =</2 .

EXPORTS
       all(Pred, List) -> bool()

	      Types  Pred = fun(Elem) -> bool()
		     Elem = term()
		     List = [term()]

	      Returns true if Pred(Elem) returns true for all elements Elem in List  ,	otherwise
	      false .

       any(Pred, List) -> bool()

	      Types  Pred = fun(Elem) -> bool()
		     Elem = term()
		     List = [term()]

	      Returns true if Pred(Elem) returns true for at least one element Elem in List .

       append(ListOfLists) -> List1

	      Types  ListOfLists = [List]
		     List = List1 = [term()]

	      Returns  a  list	in which all the sub-lists of ListOfLists have been appended. For
	      example:

	      > lists:append([[1, 2, 3], [a, b], [4, 5, 6]]).
	      [1,2,3,a,b,4,5,6]

       append(List1, List2) -> List3

	      Types  List1 = List2 = List3 = [term()]

	      Returns a new list List3 which is made from the elements of List1 followed  by  the
	      elements of List2 . For example:

	      > lists:append("abc", "def").
	      "abcdef"

	      lists:append(A, B) is equivalent to A ++ B .

       concat(Things) -> string()

	      Types  Things = [Thing]
		     Thing = atom() | integer() | float() | string()

	      Concatenates  the  text  representation of the elements of Things . The elements of
	      Things can be atoms, integers, floats or strings.

	      > lists:concat([doc, '/', file, '.', 3]).
	      "doc/file.3"

       delete(Elem, List1) -> List2

	      Types  Elem = term()
		     List1 = List2 = [term()]

	      Returns a copy of List1 where the first element matching Elem is deleted, if  there
	      is such an element.

       dropwhile(Pred, List1) -> List2

	      Types  Pred = fun(Elem) -> bool()
		     Elem = term()
		     List1 = List2 = [term()]

	      Drops  elements  Elem  from  List1  while  Pred(Elem)  returns true and returns the
	      remaining list.

       duplicate(N, Elem) -> List

	      Types  N = int()
		     Elem = term()
		     List = [term()]

	      Returns a list which contains N copies of the term Elem . For example:

	      > lists:duplicate(5, xx).
	      [xx,xx,xx,xx,xx]

       filter(Pred, List1) -> List2

	      Types  Pred = fun(Elem) -> bool()
		     Elem = term()
		     List1 = List2 = [term()]

	      List2 is a list of all elements Elem in List1 for which Pred(Elem) returns true .

       flatlength(DeepList) -> int()

	      Types  DeepList = [term() | DeepList]

	      Equivalent to length(flatten(DeepList)) , but more efficient.

       flatmap(Fun, List1) -> List2

	      Types  Fun = fun(A) -> [B]
		     List1 = [A]
		     List2 = [B]
		     A = B = term()

	      Takes a function from A s to lists of B s, and a list of A s ( List1 ) and produces
	      a  list of B s by applying the function to every element in List1 and appending the
	      resulting lists.

	      That is, flatmap behaves as if it had been defined as follows:

	      flatmap(Fun, List1) ->
		  append(map(Fun, List1)).

	      Example:

	      > lists:flatmap(fun(X)->[X,X] end, [a,b,c]).
	      [a,a,b,b,c,c]

       flatten(DeepList) -> List

	      Types  DeepList = [term() | DeepList]
		     List = [term()]

	      Returns a flattened version of DeepList .

       flatten(DeepList, Tail) -> List

	      Types  DeepList = [term() | DeepList]
		     Tail = List = [term()]

	      Returns a flattened version of DeepList with the tail Tail appended.

       foldl(Fun, Acc0, List) -> Acc1

	      Types  Fun = fun(Elem, AccIn) -> AccOut
		     Elem = term()
		     Acc0 = Acc1 = AccIn = AccOut = term()
		     List = [term()]

	      Calls Fun(Elem, AccIn) on successive elements A of List , starting  with	AccIn  ==
	      Acc0  .  Fun/2  must return a new accumulator which is passed to the next call. The
	      function returns the final value of the accumulator. Acc0 is returned if	the  list
	      is empty. For example:

	      > lists:foldl(fun(X, Sum) -> X + Sum end, 0, [1,2,3,4,5]).
	      15
	      > lists:foldl(fun(X, Prod) -> X * Prod end, 1, [1,2,3,4,5]).
	      120

       foldr(Fun, Acc0, List) -> Acc1

	      Types  Fun = fun(Elem, AccIn) -> AccOut
		     Elem = term()
		     Acc0 = Acc1 = AccIn = AccOut = term()
		     List = [term()]

	      Like foldl/3 , but the list is traversed from right to left. For example:

	      > P = fun(A, AccIn) -> io:format("~p ", [A]), AccIn end.
	      #Fun<erl_eval.12.2225172>
	      > lists:foldl(P, void, [1,2,3]).
	      1 2 3 void
	      > lists:foldr(P, void, [1,2,3]).
	      3 2 1 void

	      foldl/3 is tail recursive and would usually be preferred to foldr/3 .

       foreach(Fun, List) -> void()

	      Types  Fun = fun(Elem) -> void()
		     Elem = term()
		     List = [term()]

	      Calls  Fun(Elem) for each element Elem in List . This function is used for its side
	      effects and the evaluation order is defined to be the same as the order of the ele-
	      ments in the list.

       keydelete(Key, N, TupleList1) -> TupleList2

	      Types  Key = term()
		     N = 1..tuple_size(Tuple)
		     TupleList1 = TupleList2 = [Tuple]
		     Tuple = tuple()

	      Returns  a copy of TupleList1 where the first occurrence of a tuple whose N th ele-
	      ment compares equal to Key is deleted, if there is such a tuple.

       keyfind(Key, N, TupleList) -> Tuple | false

	      Types  Key = term()
		     N = 1..tuple_size(Tuple)
		     TupleList = [Tuple]
		     Tuple = tuple()

	      Searches the list of tuples TupleList for a tuple whose N th element compares equal
	      to Key . Returns Tuple if such a tuple is found, otherwise false .

       keymap(Fun, N, TupleList1) -> TupleList2

	      Types  Fun = fun(Term1) -> Term2
		     Term1 = Term2 = term()
		     N = 1..tuple_size(Tuple)
		     TupleList1 = TupleList2 = [tuple()]

	      Returns  a  list	of  tuples where, for each tuple in TupleList1 , the N th element
	      Term1 of the tuple has been replaced with the result of calling Fun(Term1) .

	      Examples:

	      > Fun = fun(Atom) -> atom_to_list(Atom) end.
	      #Fun<erl_eval.6.10732646>
	      2> lists:keymap(Fun, 2, [{name,jane,22},{name,lizzie,20},{name,lydia,15}]).
	      [{name,"jane",22},{name,"lizzie",20},{name,"lydia",15}]

       keymember(Key, N, TupleList) -> bool()

	      Types  Key = term()
		     N = 1..tuple_size(Tuple)
		     TupleList = [Tuple]
		     Tuple = tuple()

	      Returns true if there is a tuple in TupleList whose N th element compares equal  to
	      Key , otherwise false .

       keymerge(N, TupleList1, TupleList2) -> TupleList3

	      Types  N = 1..tuple_size(Tuple)
		     TupleList1 = TupleList2 = TupleList3 = [Tuple]
		     Tuple = tuple()

	      Returns  the sorted list formed by merging TupleList1 and TupleList2 . The merge is
	      performed on the N th element of each tuple. Both TupleList1 and TupleList2 must be
	      key-sorted  prior  to  evaluating this function. When two tuples compare equal, the
	      tuple from TupleList1 is picked before the tuple from TupleList2 .

       keyreplace(Key, N, TupleList1, NewTuple) -> TupleList2

	      Types  Key = term()
		     N = 1..tuple_size(Tuple)
		     TupleList1 = TupleList2 = [Tuple]
		     NewTuple = Tuple = tuple()

	      Returns a copy of TupleList1 where the first occurrence of a T  tuple  whose  N  th
	      element  compares equal to Key is replaced with NewTuple , if there is such a tuple
	      T .

       keysearch(Key, N, TupleList) -> {value, Tuple} | false

	      Types  Key = term()
		     N = 1..tuple_size(Tuple)
		     TupleList = [Tuple]
		     Tuple = tuple()

	      Searches the list of tuples TupleList for a tuple whose N th element compares equal
	      to Key . Returns {value, Tuple} if such a tuple is found, otherwise false .

   Note:
       This function is retained for backward compatibility. The function lists:keyfind/3 (intro-
       duced in R13A) is in most cases more convenient.

       keysort(N, TupleList1) -> TupleList2

	      Types  N = 1..tuple_size(Tuple)
		     TupleList1 = TupleList2 = [Tuple]
		     Tuple = tuple()

	      Returns a list containing the sorted elements of the list TupleList1 .  Sorting  is
	      performed on the N th element of the tuples. The sort is stable.

       keystore(Key, N, TupleList1, NewTuple) -> TupleList2

	      Types  Key = term()
		     N = 1..tuple_size(Tuple)
		     TupleList1 = TupleList2 = [Tuple]
		     NewTuple = Tuple = tuple()

	      Returns  a  copy	of  TupleList1 where the first occurrence of a tuple T whose N th
	      element compares equal to Key is replaced with NewTuple , if there is such a  tuple
	      T  .  If	there is no such tuple T a copy of TupleList1 where [ NewTuple ] has been
	      appended to the end is returned.

       keytake(Key, N, TupleList1) -> {value, Tuple, TupleList2} | false

	      Types  Key = term()
		     N = 1..tuple_size(Tuple)
		     TupleList1 = TupleList2 = [Tuple]
		     Tuple = tuple()

	      Searches the list of tuples TupleList1 for a tuple  whose  N  th	element  compares
	      equal  to Key . Returns {value, Tuple, TupleList2} if such a tuple is found, other-
	      wise false . TupleList2 is a copy of TupleList1 where the first occurrence of Tuple
	      has been removed.

       last(List) -> Last

	      Types  List = [term()], length(List) > 0
		     Last = term()

	      Returns the last element in List .

       map(Fun, List1) -> List2

	      Types  Fun = fun(A) -> B
		     List1 = [A]
		     List2 = [B]
		     A = B = term()

	      Takes  a	function from A s to B s, and a list of A s and produces a list of B s by
	      applying the function to every element in the list. This function is used to obtain
	      the return values. The evaluation order is implementation dependent.

       mapfoldl(Fun, Acc0, List1) -> {List2, Acc1}

	      Types  Fun = fun(A, AccIn) -> {B, AccOut}
		     Acc0 = Acc1 = AccIn = AccOut = term()
		     List1 = [A]
		     List2 = [B]
		     A = B = term()

	      mapfoldl	combines  the  operations of map/2 and foldl/3 into one pass. An example,
	      summing the elements in a list and double them at the same time:

	      > lists:mapfoldl(fun(X, Sum) -> {2*X, X+Sum} end,
	      0, [1,2,3,4,5]).
	      {[2,4,6,8,10],15}

       mapfoldr(Fun, Acc0, List1) -> {List2, Acc1}

	      Types  Fun = fun(A, AccIn) -> {B, AccOut}
		     Acc0 = Acc1 = AccIn = AccOut = term()
		     List1 = [A]
		     List2 = [B]
		     A = B = term()

	      mapfoldr combines the operations of map/2 and foldr/3 into one pass.

       max(List) -> Max

	      Types  List = [term()], length(List) > 0
		     Max = term()

	      Returns the first element of List that compares greater than or equal to all  other
	      elements of List .

       member(Elem, List) -> bool()

	      Types  Elem = term()
		     List = [term()]

	      Returns true if Elem matches some element of List , otherwise false .

       merge(ListOfLists) -> List1

	      Types  ListOfLists = [List]
		     List = List1 = [term()]

	      Returns  the  sorted  list formed by merging all the sub-lists of ListOfLists . All
	      sub-lists must be sorted prior to evaluating this function. When two elements  com-
	      pare  equal,  the element from the sub-list with the lowest position in ListOfLists
	      is picked before the other element.

       merge(List1, List2) -> List3

	      Types  List1 = List2 = List3 = [term()]

	      Returns the sorted list formed by merging List1 and List2 . Both	List1  and  List2
	      must  be sorted prior to evaluating this function. When two elements compare equal,
	      the element from List1 is picked before the element from List2 .

       merge(Fun, List1, List2) -> List3

	      Types  Fun = fun(A, B) -> bool()
		     List1 = [A]
		     List2 = [B]
		     List3 = [A | B]
		     A = B = term()

	      Returns the sorted list formed by merging List1 and List2 . Both	List1  and  List2
	      must  be	sorted	according  to  the ordering function Fun prior to evaluating this
	      function. Fun(A, B) should return true if A compares less than or equal to B in the
	      ordering,  false otherwise. When two elements compare equal, the element from List1
	      is picked before the element from List2 .

       merge3(List1, List2, List3) -> List4

	      Types  List1 = List2 = List3 = List4 = [term()]

	      Returns the sorted list formed by merging List1 , List2 and List3 . All of List1	,
	      List2 and List3 must be sorted prior to evaluating this function. When two elements
	      compare equal, the element from List1 , if there is  such  an  element,  is  picked
	      before  the  other  element,  otherwise the element from List2 is picked before the
	      element from List3 .

       min(List) -> Min

	      Types  List = [term()], length(List) > 0
		     Min = term()

	      Returns the first element of List that compares less than or  equal  to  all  other
	      elements of List .

       nth(N, List) -> Elem

	      Types  N = 1..length(List)
		     List = [term()]
		     Elem = term()

	      Returns the N th element of List . For example:

	      > lists:nth(3, [a, b, c, d, e]).
	      c

       nthtail(N, List1) -> Tail

	      Types  N = 0..length(List1)
		     List1 = Tail = [term()]

	      Returns  the  N  th tail of List , that is, the sublist of List starting at N+1 and
	      continuing up to the end of the list. For example:

	      > lists:nthtail(3, [a, b, c, d, e]).
	      [d,e]
	      > tl(tl(tl([a, b, c, d, e]))).
	      [d,e]
	      > lists:nthtail(0, [a, b, c, d, e]).
	      [a,b,c,d,e]
	      > lists:nthtail(5, [a, b, c, d, e]).
	      []

       partition(Pred, List) -> {Satisfying, NonSatisfying}

	      Types  Pred = fun(Elem) -> bool()
		     Elem = term()
		     List = Satisfying = NonSatisfying = [term()]

	      Partitions List into two lists, where the first  list  contains  all  elements  for
	      which Pred(Elem) returns true , and the second list contains all elements for which
	      Pred(Elem) returns false .

	      Examples:

	      > lists:partition(fun(A) -> A rem 2 == 1 end, [1,2,3,4,5,6,7]).
	      {[1,3,5,7],[2,4,6]}
	      > lists:partition(fun(A) -> is_atom(A) end, [a,b,1,c,d,2,3,4,e]).
	      {[a,b,c,d,e],[1,2,3,4]}

	      See also splitwith/2 for a different way to partition a list.

       prefix(List1, List2) -> bool()

	      Types  List1 = List2 = [term()]

	      Returns true if List1 is a prefix of List2 , otherwise false .

       reverse(List1) -> List2

	      Types  List1 = List2 = [term()]

	      Returns a list with the top level elements in List1 in reverse order.

       reverse(List1, Tail) -> List2

	      Types  List1 = Tail = List2 = [term()]

	      Returns a list with the top level elements in List1 in reverse order, with the tail
	      Tail appended. For example:

	      > lists:reverse([1, 2, 3, 4], [a, b, c]).
	      [4,3,2,1,a,b,c]

       seq(From, To) -> Seq
       seq(From, To, Incr) -> Seq

	      Types  From = To = Incr = int()
		     Seq = [int()]

	      Returns  a  sequence of integers which starts with From and contains the successive
	      results of adding Incr to the previous element, until To has been reached or passed
	      (in the latter case, To is not an element of the sequence). Incr defaults to 1.

	      Failure: If To<From-Incr and Incr is positive, or if To>From-Incr and Incr is nega-
	      tive, or if Incr==0 and From/=To .

	      The following equalities hold for all sequences:

	      length(lists:seq(From, To)) == To-From+1
	      length(lists:seq(From, To, Incr)) == (To-From+Incr) div Incr

	      Examples:

	      > lists:seq(1, 10).
	      [1,2,3,4,5,6,7,8,9,10]
	      > lists:seq(1, 20, 3).
	      [1,4,7,10,13,16,19]
	      > lists:seq(1, 0, 1).
	      []
	      > lists:seq(10, 6, 4).
	      []
	      > lists:seq(1, 1, 0).
	      [1]

       sort(List1) -> List2

	      Types  List1 = List2 = [term()]

	      Returns a list containing the sorted elements of List1 .

       sort(Fun, List1) -> List2

	      Types  Fun = fun(Elem1, Elem2) -> bool()
		     Elem1 = Elem2 = term()
		     List1 = List2 = [term()]

	      Returns a list containing the sorted elements of List1 , according to the  ordering
	      function	Fun  . Fun(A, B) should return true if A compares less than or equal to B
	      in the ordering, false otherwise.

       split(N, List1) -> {List2, List3}

	      Types  N = 0..length(List1)
		     List1 = List2 = List3 = [term()]

	      Splits List1 into List2 and List3 . List2 contains the first N elements  and  List3
	      the rest of the elements (the N th tail).

       splitwith(Pred, List) -> {List1, List2}

	      Types  Pred = fun(Elem) -> bool()
		     Elem = term()
		     List = List1 = List2 = [term()]

	      Partitions  List into two lists according to Pred . splitwith/2 behaves as if it is
	      defined as follows:

	      splitwith(Pred, List) ->
		  {takewhile(Pred, List), dropwhile(Pred, List)}.

	      Examples:

	      > lists:splitwith(fun(A) -> A rem 2 == 1 end, [1,2,3,4,5,6,7]).
	      {[1],[2,3,4,5,6,7]}
	      > lists:splitwith(fun(A) -> is_atom(A) end, [a,b,1,c,d,2,3,4,e]).
	      {[a,b],[1,c,d,2,3,4,e]}

	      See also partition/2 for a different way to partition a list.

       sublist(List1, Len) -> List2

	      Types  List1 = List2 = [term()]
		     Len = int()

	      Returns the sub-list of List1 starting at position 1 and with (max)  Len	elements.
	      It  is  not  an  error for Len to exceed the length of the list -- in that case the
	      whole list is returned.

       sublist(List1, Start, Len) -> List2

	      Types  List1 = List2 = [term()]
		     Start = 1..(length(List1)+1)
		     Len = int()

	      Returns the sub-list of List1 starting at Start and with (max) Len elements. It  is
	      not an error for Start+Len to exceed the length of the list.

	      > lists:sublist([1,2,3,4], 2, 2).
	      [2,3]
	      > lists:sublist([1,2,3,4], 2, 5).
	      [2,3,4]
	      > lists:sublist([1,2,3,4], 5, 2).
	      []

       subtract(List1, List2) -> List3

	      Types  List1 = List2 = List3 = [term()]

	      Returns a new list List3 which is a copy of List1 , subjected to the following pro-
	      cedure: for each element in List2 , its first occurrence in List1 is  deleted.  For
	      example:

	      > lists:subtract("123212", "212").
	      "312".

	      lists:subtract(A, B) is equivalent to A -- B .

   Warning:
       The  complexity	of  lists:subtract(A, B) is proportional to length(A)*length(B) , meaning
       that it will be very slow if both A and B are long lists. (Using ordered  lists	and  ord-
       sets:subtract/2 is a much better choice if both lists are long.)

       suffix(List1, List2) -> bool()

	      Returns true if List1 is a suffix of List2 , otherwise false .

       sum(List) -> number()

	      Types  List = [number()]

	      Returns the sum of the elements in List .

       takewhile(Pred, List1) -> List2

	      Types  Pred = fun(Elem) -> bool()
		     Elem = term()
		     List1 = List2 = [term()]

	      Takes  elements  Elem from List1 while Pred(Elem) returns true , that is, the func-
	      tion returns the longest prefix of the list for  which  all  elements  satisfy  the
	      predicate.

       ukeymerge(N, TupleList1, TupleList2) -> TupleList3

	      Types  N = 1..tuple_size(Tuple)
		     TupleList1 = TupleList2 = TupleList3 = [Tuple]
		     Tuple = tuple()

	      Returns  the sorted list formed by merging TupleList1 and TupleList2 . The merge is
	      performed on the N th element of each tuple. Both TupleList1 and TupleList2 must be
	      key-sorted  without  duplicates  prior to evaluating this function. When two tuples
	      compare equal, the tuple from TupleList1 is picked  and  the  one  from  TupleList2
	      deleted.

       ukeysort(N, TupleList1) -> TupleList2

	      Types  N = 1..tuple_size(Tuple)
		     TupleList1 = TupleList2 = [Tuple]
		     Tuple = tuple()

	      Returns  a list containing the sorted elements of the list TupleList1 where all but
	      the first tuple of the tuples comparing equal have been deleted.	Sorting  is  per-
	      formed on the N th element of the tuples.

       umerge(ListOfLists) -> List1

	      Types  ListOfLists = [List]
		     List = List1 = [term()]

	      Returns  the  sorted  list formed by merging all the sub-lists of ListOfLists . All
	      sub-lists must be sorted and contain no duplicates prior to evaluating  this  func-
	      tion.  When two elements compare equal, the element from the sub-list with the low-
	      est position in ListOfLists is picked and the other one deleted.

       umerge(List1, List2) -> List3

	      Types  List1 = List2 = List3 = [term()]

	      Returns the sorted list formed by merging List1 and List2 . Both	List1  and  List2
	      must  be	sorted	and contain no duplicates prior to evaluating this function. When
	      two elements compare equal, the element from List1 is picked and the one from List2
	      deleted.

       umerge(Fun, List1, List2) -> List3

	      Types  Fun = fun(A, B) -> bool()
		     List1 = [A]
		     List2 = [B]
		     List3 = [A | B]
		     A = B = term()

	      Returns  the  sorted  list formed by merging List1 and List2 . Both List1 and List2
	      must be sorted according to the ordering function Fun  and  contain  no  duplicates
	      prior  to evaluating this function. Fun(A, B) should return true if A compares less
	      than or equal to B in the ordering, false  otherwise.  When  two	elements  compare
	      equal, the element from List1 is picked and the one from List2 deleted.

       umerge3(List1, List2, List3) -> List4

	      Types  List1 = List2 = List3 = List4 = [term()]

	      Returns  the sorted list formed by merging List1 , List2 and List3 . All of List1 ,
	      List2 and List3 must be sorted and contain no duplicates prior to  evaluating  this
	      function.  When  two  elements  compare  equal, the element from List1 is picked if
	      there is such an element, otherwise the element from List2 is picked, and the other
	      one deleted.

       unzip(List1) -> {List2, List3}

	      Types  List1 = [{X, Y}]
		     List2 = [X]
		     List3 = [Y]
		     X = Y = term()

	      "Unzips"	a  list  of  two-tuples into two lists, where the first list contains the
	      first element of each tuple, and the second list contains  the  second  element  of
	      each tuple.

       unzip3(List1) -> {List2, List3, List4}

	      Types  List1 = [{X, Y, Z}]
		     List2 = [X]
		     List3 = [Y]
		     List4 = [Z]
		     X = Y = Z = term()

	      "Unzips" a list of three-tuples into three lists, where the first list contains the
	      first element of each tuple, the second list contains the second	element  of  each
	      tuple, and the third list contains the third element of each tuple.

       usort(List1) -> List2

	      Types  List1 = List2 = [term()]

	      Returns a list containing the sorted elements of List1 where all but the first ele-
	      ment of the elements comparing equal have been deleted.

       usort(Fun, List1) -> List2

	      Types  Fun = fun(Elem1, Elem2) -> bool()
		     Elem1 = Elem2 = term()
		     List1 = List2 = [term()]

	      Returns a list which contains the sorted elements of List1 where all but the  first
	      element of the elements comparing equal according to the ordering function Fun have
	      been deleted. Fun(A, B) should return true if A compares less than or equal to B in
	      the ordering, false otherwise.

       zip(List1, List2) -> List3

	      Types  List1 = [X]
		     List2 = [Y]
		     List3 = [{X, Y}]
		     X = Y = term()

	      "Zips"  two lists of equal length into one list of two-tuples, where the first ele-
	      ment of each tuple is taken from the first list and the  second  element	is  taken
	      from corresponding element in the second list.

       zip3(List1, List2, List3) -> List4

	      Types  List1 = [X]
		     List2 = [Y]
		     List3 = [Z]
		     List3 = [{X, Y, Z}]
		     X = Y = Z = term()

	      "Zips"  three  lists of equal length into one list of three-tuples, where the first
	      element of each tuple is taken from the first list, the  second  element	is  taken
	      from  corresponding element in the second list, and the third element is taken from
	      the corresponding element in the third list.

       zipwith(Combine, List1, List2) -> List3

	      Types  Combine = fun(X, Y) -> T
		     List1 = [X]
		     List2 = [Y]
		     List3 = [T]
		     X = Y = T = term()

	      Combine the elements of two lists of equal length into one list. For each pair X, Y
	      of  list	elements  from the two lists, the element in the result list will be Com-
	      bine(X, Y) .

	      zipwith(fun(X, Y) -> {X,Y} end, List1, List2) is equivalent to zip(List1, List2) .

	      Example:

	      > lists:zipwith(fun(X, Y) -> X+Y end, [1,2,3], [4,5,6]).
	      [5,7,9]

       zipwith3(Combine, List1, List2, List3) -> List4

	      Types  Combine = fun(X, Y, Z) -> T
		     List1 = [X]
		     List2 = [Y]
		     List3 = [Z]
		     List4 = [T]
		     X = Y = Z = T = term()

	      Combine the elements of three lists of equal length into one list. For each  triple
	      X,  Y, Z of list elements from the three lists, the element in the result list will
	      be Combine(X, Y, Z) .

	      zipwith3(fun(X, Y, Z) ->	{X,Y,Z}  end,  List1,  List2,  List3)  is  equivalent  to
	      zip3(List1, List2, List3) .

	      Examples:

	      > lists:zipwith3(fun(X, Y, Z) -> X+Y+Z end, [1,2,3], [4,5,6], [7,8,9]).
	      [12,15,18]
	      > lists:zipwith3(fun(X, Y, Z) -> [X,Y,Z] end, [a,b,c], [x,y,z], [1,2,3]).
	      [[a,x,1],[b,y,2],[c,z,3]]

Ericsson AB				  stdlib 1.17.3 			      lists(3erl)


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