diff options
Diffstat (limited to 'lib/stdlib/src/lists.erl')
| -rw-r--r-- | lib/stdlib/src/lists.erl | 57 |
1 files changed, 43 insertions, 14 deletions
diff --git a/lib/stdlib/src/lists.erl b/lib/stdlib/src/lists.erl index b5577165f4..af9d63ddd6 100644 --- a/lib/stdlib/src/lists.erl +++ b/lib/stdlib/src/lists.erl @@ -1,18 +1,19 @@ %% %% %CopyrightBegin% %% -%% Copyright Ericsson AB 1996-2013. All Rights Reserved. +%% Copyright Ericsson AB 1996-2016. All Rights Reserved. %% -%% The contents of this file are subject to the Erlang Public License, -%% Version 1.1, (the "License"); you may not use this file except in -%% compliance with the License. You should have received a copy of the -%% Erlang Public License along with this software. If not, it can be -%% retrieved online at http://www.erlang.org/. +%% Licensed under the Apache License, Version 2.0 (the "License"); +%% you may not use this file except in compliance with the License. +%% You may obtain a copy of the License at %% -%% Software distributed under the License is distributed on an "AS IS" -%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See -%% the License for the specific language governing rights and limitations -%% under the License. +%% http://www.apache.org/licenses/LICENSE-2.0 +%% +%% Unless required by applicable law or agreed to in writing, software +%% distributed under the License is distributed on an "AS IS" BASIS, +%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +%% See the License for the specific language governing permissions and +%% limitations under the License. %% %% %CopyrightEnd% %% @@ -22,7 +23,7 @@ -compile({no_auto_import,[min/2]}). -export([append/2, append/1, subtract/2, reverse/1, - nth/2, nthtail/2, prefix/2, suffix/2, last/1, + nth/2, nthtail/2, prefix/2, suffix/2, droplast/1, last/1, seq/2, seq/3, sum/1, duplicate/2, min/1, max/1, sublist/2, sublist/3, delete/2, unzip/1, unzip3/1, zip/2, zip3/3, zipwith/3, zipwith3/4, @@ -38,7 +39,8 @@ -export([all/2,any/2,map/2,flatmap/2,foldl/3,foldr/3,filter/2, partition/2,zf/2,filtermap/2, mapfoldl/3,mapfoldr/3,foreach/2,takewhile/2,dropwhile/2,splitwith/2, - split/2]). + split/2, + join/2]). %%% BIFs -export([keyfind/3, keymember/3, keysearch/3, member/2, reverse/2]). @@ -203,6 +205,19 @@ suffix(Suffix, List) -> Delta = length(List) - length(Suffix), Delta >= 0 andalso nthtail(Delta, List) =:= Suffix. +%% droplast(List) returns the list dropping its last element + +-spec droplast(List) -> InitList when + List :: [T, ...], + InitList :: [T], + T :: term(). + +%% This is the simple recursive implementation +%% reverse(tl(reverse(L))) is faster on average, +%% but creates more garbage. +droplast([_T]) -> []; +droplast([H|T]) -> [H|droplast(T)]. + %% last(List) returns the last element in a list. -spec last(List) -> Last when @@ -630,7 +645,7 @@ flatlength([H|T], L) when is_list(H) -> flatlength([_|T], L) -> flatlength(T, L + 1); flatlength([], L) -> L. - + %% keymember(Key, Index, [Tuple]) Now a BIF! %% keyfind(Key, Index, [Tuple]) A BIF! %% keysearch(Key, Index, [Tuple]) Now a BIF! @@ -1163,7 +1178,7 @@ rumerge(T1, []) -> T1; rumerge(T1, [H2 | T2]) -> lists:reverse(rumerge2_1(T1, T2, [], H2), []). - + %% all(Predicate, List) %% any(Predicate, List) %% map(Function, List) @@ -1425,6 +1440,18 @@ split(N, [H|T], R) -> split(_, [], _) -> badarg. +-spec join(Sep, List1) -> List2 when + Sep :: T, + List1 :: [T], + List2 :: [T], + T :: term(). + +join(_Sep, []) -> []; +join(Sep, [H|T]) -> [H|join_prepend(Sep, T)]. + +join_prepend(_Sep, []) -> []; +join_prepend(Sep, [H|T]) -> [Sep,H|join_prepend(Sep,T)]. + %%% ================================================================= %%% Here follows the implementation of the sort functions. %%% @@ -2253,6 +2280,8 @@ ukeysplit_2(I, Y, EY, [Z | L], R) -> ukeysplit_2(_I, Y, _EY, [], R) -> [Y | R]. +-dialyzer({no_improper_lists, ukeymergel/3}). + ukeymergel(I, [T1, [H2 | T2], [H3 | T3] | L], Acc) -> %% The fourth argument, [H2 | H3] (=HdM), may confuse type %% checkers. Its purpose is to ensure that the tests H2 == HdM |