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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) -> boolean()

Types:

Pred = fun((Elem :: T) -> boolean())
List = [T]
T = term()

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

any(Pred, List) -> boolean()

Types:

Pred = fun((Elem :: T) -> boolean())
List = [T]
T = term()

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

append(ListOfLists) -> List1

Types:

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

Returns a list in which all the sublists of ListOfLists have been appended.

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 = [T]
T = term()

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

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.

Example:

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

delete(Elem, List1) -> List2

Types:

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

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

droplast(List) -> InitList

Types:

List = [T, ...]
InitList = [T]
T = term()

Drops the last element of a List. The  list  is  to  be  non-empty,  otherwise  the
function crashes with a function_clause.

dropwhile(Pred, List1) -> List2

Types:

Pred = fun((Elem :: T) -> boolean())
List1 = List2 = [T]
T = term()

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

duplicate(N, Elem) -> List

Types:

N = integer() >= 0
Elem = T
List = [T]
T = term()

Returns a list containing N copies of term Elem.

Example:

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

filter(Pred, List1) -> List2

Types:

Pred = fun((Elem :: T) -> boolean())
List1 = List2 = [T]
T = term()

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

filtermap(Fun, List1) -> List2

Types:

Fun = fun((Elem) -> boolean() | {true, Value})
List1 = [Elem]
List2 = [Elem | Value]
Elem = Value = term()

Calls Fun(Elem) on successive elements Elem of List1. Fun/1 must  return  either  a
Boolean  or  a  tuple  {true, Value}. The function returns the list of elements for
which Fun returns a new value, where a value of  true  is  synonymous  with  {true,
Elem}.

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

filtermap(Fun, List1) ->
lists:foldr(fun(Elem, Acc) ->
case Fun(Elem) of
false -> Acc;
true -> [Elem|Acc];
{true,Value} -> [Value|Acc]
end
end, [], List1).

Example:

> lists:filtermap(fun(X) -> case X rem 2 of 0 -> {true, X div 2}; _ -> false end end, [1,2,3,4,5]).
[1,2]

flatlength(DeepList) -> integer() >= 0

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 As to lists of Bs, and a list of As (List1) and produces a
list of Bs 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 tail Tail appended.

foldl(Fun, Acc0, List) -> Acc1

Types:

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

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 :: T, AccIn) -> AccOut)
Acc0 = Acc1 = AccIn = AccOut = term()
List = [T]
T = term()

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

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 is usually preferred to foldr/3.

join(Sep, List1) -> List2

Types:

Sep = T
List1 = List2 = [T]
T = term()

Inserts Sep between each element in List1. Has no effect on the empty list and on a
singleton list. For example:

> lists:join(x, [a,b,c]).
[a,x,b,x,c]
> lists:join(x, [a]).
[a]
> lists:join(x, []).
[]

foreach(Fun, List) -> ok

Types:

Fun = fun((Elem :: T) -> term())
List = [T]
T = 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
elements in the list.

keydelete(Key, N, TupleList1) -> TupleList2

Types:

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

Returns  a  copy  of  TupleList1  where  the  first occurrence of a tuple whose Nth
element compares equal to Key is deleted, if there is such a tuple.

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

Types:

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

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

keymap(Fun, N, TupleList1) -> TupleList2

Types:

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

Returns a list of tuples where, for each tuple in TupleList1, the Nth 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) -> boolean()

Types:

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

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

keymerge(N, TupleList1, TupleList2) -> TupleList3

Types:

N = integer() >= 1
1..tuple_size(Tuple)
TupleList1 = [T1]
TupleList2 = [T2]
TupleList3 = [T1 | T2]
T1 = T2 = Tuple
Tuple = tuple()

Returns  the  sorted list formed by merging TupleList1 and TupleList2. The merge is
performed on the Nth element of each tuple. Both TupleList1 and TupleList2 must  be
key-sorted  before  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 = integer() >= 1
1..tuple_size(Tuple)
TupleList1 = TupleList2 = [Tuple]
NewTuple = Tuple
Tuple = tuple()

Returns a copy of TupleList1 where the first occurrence of  a  T  tuple  whose  Nth
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 = integer() >= 1
1..tuple_size(Tuple)
TupleList = [Tuple]
Tuple = tuple()

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

Note:
This function is retained for backward compatibility. Function keyfind/3 is usually
more convenient.

keysort(N, TupleList1) -> TupleList2

Types:

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

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

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

Types:

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

Returns  a  copy  of  TupleList1  where the first occurrence of a tuple T whose Nth
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 = integer() >= 1
1..tuple_size(Tuple)
TupleList1 = TupleList2 = [tuple()]
Tuple = tuple()

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

last(List) -> Last

Types:

List = [T, ...]
Last = T
T = 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  As  to  Bs, and a list of As and produces a list of Bs by
applying the function to every element in the list. This function is used to obtain
the return values. The evaluation order depends on the implementation.

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()

Combines the operations of map/2 and foldl/3 into one pass.

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()

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

max(List) -> Max

Types:

List = [T, ...]
Max = T
T = term()

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

member(Elem, List) -> boolean()

Types:

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

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

merge(ListOfLists) -> List1

Types:

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

Returns the sorted list formed by merging all  the  sublists  of  ListOfLists.  All
sublists  must be sorted before evaluating this function. When two elements compare
equal, the element from the sublist with the  lowest  position  in  ListOfLists  is
picked before the other element.

merge(List1, List2) -> List3

Types:

List1 = [X]
List2 = [Y]
List3 = [X | Y]
X = Y = term()

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

merge3(List1, List2, List3) -> List4

Types:

List1 = [X]
List2 = [Y]
List3 = [Z]
List4 = [X | Y | Z]
X = Y = Z = term()

Returns  the  sorted  list formed by merging List1, List2, and List3. All of List1,
List2, and List3 must be sorted before 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 = [T, ...]
Min = T
T = 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 = integer() >= 1
1..length(List)
List = [T, ...]
Elem = T
T = term()

Returns the Nth element of List.

Example:

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

nthtail(N, List) -> Tail

Types:

N = integer() >= 0
0..length(List)
List = [T, ...]
Tail = [T]
T = term()

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

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, NotSatisfying}

Types:

Pred = fun((Elem :: T) -> boolean())
List = Satisfying = NotSatisfying = [T]
T = 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]}

For a different way to partition a list, see splitwith/2.

prefix(List1, List2) -> boolean()

Types:

List1 = List2 = [T]
T = term()

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

reverse(List1) -> List2

Types:

List1 = List2 = [T]
T = term()

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

reverse(List1, Tail) -> List2

Types:

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

Returns  a  list  with  the  elements  in  List1  in  reverse order, with tail Tail
appended.

Example:

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

search(Pred, List) -> {value, Value} | false

Types:

Pred = fun((T) -> boolean())
List = [T]
Value = T

If there is a Value in List such that Pred(Value)  returns  true,  returns  {value,
Value} for the first such Value, otherwise returns false.

seq(From, To) -> Seq

seq(From, To, Incr) -> Seq

Types:

From = To = Incr = integer()
Seq = [integer()]

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

Failures:

* If To < From - Incr and Incr > 0.

* If To > From - Incr and Incr < 0.

* 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).


sort(List1) -> List2

Types:

List1 = List2 = [T]
T = term()

Returns a list containing the sorted elements of List1.

sort(Fun, List1) -> List2

Types:

Fun = fun((A :: T, B :: T) -> boolean())
List1 = List2 = [T]
T = term()

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

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

Types:

N = integer() >= 0
0..length(List1)
List1 = List2 = List3 = [T]
T = term()

Splits  List1  into  List2 and List3. List2 contains the first N elements and List3
the remaining elements (the Nth tail).

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

Types:

Pred = fun((T) -> boolean())
List = List1 = List2 = [T]
T = 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]).
{,[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]}

For a different way to partition a list, see partition/2.

sublist(List1, Len) -> List2

Types:

List1 = List2 = [T]
Len = integer() >= 0
T = term()

Returns  the  sublist  of  List1  starting  at  position  1  and with (maximum) 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 = [T]
Start = integer() >= 1
1..(length(List1)+1)
Len = integer() >= 0
T = term()

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

Examples:

> 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 = [T]
T = term()

Returns a new list List3 that is a  copy  of  List1,  subjected  to  the  following
procedure: for each element in List2, its first occurrence in List1 is deleted.

Example:

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

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

suffix(List1, List2) -> boolean()

Types:

List1 = List2 = [T]
T = term()

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 :: T) -> boolean())
List1 = List2 = [T]
T = term()

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

ukeymerge(N, TupleList1, TupleList2) -> TupleList3

Types:

N = integer() >= 1
1..tuple_size(Tuple)
TupleList1 = [T1]
TupleList2 = [T2]
TupleList3 = [T1 | T2]
T1 = T2 = Tuple
Tuple = tuple()

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

ukeysort(N, TupleList1) -> TupleList2

Types:

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

Returns  a  list containing the sorted elements of list TupleList1 where all except
the first tuple of the  tuples  comparing  equal  have  been  deleted.  Sorting  is
performed on the Nth element of the tuples.

umerge(ListOfLists) -> List1

Types:

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

Returns  the  sorted  list  formed  by merging all the sublists of ListOfLists. All
sublists must be sorted and contain no duplicates before evaluating this  function.
When  two  elements  compare  equal,  the  element from the sublist with the lowest
position in ListOfLists is picked and the other is deleted.

umerge(List1, List2) -> List3

Types:

List1 = [X]
List2 = [Y]
List3 = [X | Y]
X = Y = term()

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

umerge(Fun, List1, List2) -> List3

Types:

Fun = fun((A, B) -> boolean())
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
before  evaluating  this  function.  Fun(A, B) is to return true if A compares less
than or equal to B in the ordering, otherwise  false.  When  two  elements  compare
equal, the element from List1 is picked and the one from List2 is deleted.

umerge3(List1, List2, List3) -> List4

Types:

List1 = [X]
List2 = [Y]
List3 = [Z]
List4 = [X | Y | Z]
X = Y = Z = 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  before  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
is deleted.

unzip(List1) -> {List2, List3}

Types:

List1 = [{A, B}]
List2 = [A]
List3 = [B]
A = B = 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 = [{A, B, C}]
List2 = [A]
List3 = [B]
List4 = [C]
A = B = C = 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 = [T]
T = term()

Returns  a  list containing the sorted elements of List1 where all except the first
element of the elements comparing equal have been deleted.

usort(Fun, List1) -> List2

Types:

Fun = fun((T, T) -> boolean())
List1 = List2 = [T]
T = term()

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

zip(List1, List2) -> List3

Types:

List1 = [A]
List2 = [B]
List3 = [{A, B}]
A = B = term()

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

zip3(List1, List2, List3) -> List4

Types:

List1 = [A]
List2 = [B]
List3 = [C]
List4 = [{A, B, C}]
A = B = C = 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  the  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()

Combines 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 is Combine(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()

Combines 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 is
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]]