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5081-Add-lists-enumerate-1-and-lists-enumerate-...
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File 5081-Add-lists-enumerate-1-and-lists-enumerate-2.patch of Package erlang
From 0aef479c4fb9eb31f7c3e9edac601f52288426fd Mon Sep 17 00:00:00 2001 From: radrow <radrowicki@gmail.com> Date: Wed, 2 Jun 2021 14:06:44 +0200 Subject: [PATCH] Add lists:enumerate/1 and lists:enumerate/2 This commit introduces `enumerate/1` and `enumerate/2` functions to the `lists` module in standard library. Simple unit tests and documentation for the introduced functions are included. Fix test Equalities in docs Better binary test Change the definition example change the definition example back to mapfoldl Remove unnecessary parens Co-authored-by: Lukas Larsson <garazdawi@gmail.com> Fix test result --- lib/stdlib/doc/src/lists.xml | 42 +++++++++++++++++++++++++++++++++ lib/stdlib/src/lists.erl | 20 +++++++++++++++- lib/stdlib/test/lists_SUITE.erl | 20 ++++++++++++++-- 3 files changed, 79 insertions(+), 3 deletions(-) diff --git a/lib/stdlib/doc/src/lists.xml b/lib/stdlib/doc/src/lists.xml index 5477f13d1e..ad60829e72 100644 --- a/lib/stdlib/doc/src/lists.xml +++ b/lib/stdlib/doc/src/lists.xml @@ -174,6 +174,48 @@ </desc> </func> + <func> + <name name="enumerate" arity="1" since="OTP 25.0"/> + <fsummary>Annotates elements with their index.</fsummary> + <desc> + <p>Returns <c><anno>List1</anno></c> with each element + <c>H</c> replaced by a tuple of form <c>{I, H}</c> where + <c>I</c> is the position of <c>H</c> in + <c><anno>List1</anno></c>. The enumeration starts with 1 and + increases by 1 in each step.</p> + <p>That is, <c>enumerate/1</c> behaves as if it had been defined as follows:</p> + <code type="erl"> +enumerate(List) -> + {List1, _ } = lists:mapfoldl(fun(T, Acc) -> {{Acc, T}, Acc+1} end, 1, List), + List1.</code> + <p><em>Example:</em></p> + <pre> +> <input>lists:enumerate([a,b,c]).</input> +[{1,a},{2,b},{3,c}]</pre> + </desc> + </func> + + <func> + <name name="enumerate" arity="2" since="OTP 25.0"/> + <fsummary>Annotates elements with their index.</fsummary> + <desc> + <p>Returns <c><anno>List1</anno></c> with each element + <c>H</c> replaced by a tuple of form <c>{I, H}</c> where + <c>I</c> is the position of <c>H</c> in + <c><anno>List1</anno></c>. The enumeration starts with + <c><anno>Index</anno></c> and increases by 1 in each step.</p> + <p>That is, <c>enumerate/2</c> behaves as if it had been defined as follows:</p> + <code type="erl"> +enumerate(I, List) -> + {List1, _ } = lists:mapfoldl(fun(T, Acc) -> {{Acc, T}, Acc+1} end, I, List), + List1.</code> + <p><em>Example:</em></p> + <pre> +> <input>lists:enumerate(10, [a,b,c]).</input> +[{10,a},{11,b},{12,c}]</pre> + </desc> + </func> + <func> <name name="filter" arity="2" since=""/> <fsummary>Select elements that satisfy a predicate.</fsummary> diff --git a/lib/stdlib/src/lists.erl b/lib/stdlib/src/lists.erl index f44ed726ca..b82732e0ca 100644 --- a/lib/stdlib/src/lists.erl +++ b/lib/stdlib/src/lists.erl @@ -32,7 +32,7 @@ concat/1, flatten/1, flatten/2, flatlength/1, keydelete/3, keyreplace/4, keytake/3, keystore/4, keysort/2, keymerge/3, rkeymerge/3, rukeymerge/3, - ukeysort/2, ukeymerge/3, keymap/3]). + ukeysort/2, ukeymerge/3, keymap/3, enumerate/1, enumerate/2]). -export([merge/3, rmerge/3, sort/2, umerge/3, rumerge/3, usort/2]). @@ -957,6 +957,24 @@ keymap(Fun, Index, [Tup|Tail]) -> keymap(Fun, Index, []) when is_integer(Index), Index >= 1, is_function(Fun, 1) -> []. +-spec enumerate(List1) -> List2 when + List1 :: [T], + List2 :: [{Index, T}], + Index :: integer(), + T :: term(). +enumerate(List1) -> + enumerate(1, List1). + +-spec enumerate(Index, List1) -> List2 when + List1 :: [T], + List2 :: [{Index, T}], + Index :: integer(), + T :: term(). +enumerate(Index, [H|T]) when is_integer(Index) -> + [{Index, H}|enumerate(Index + 1, T)]; +enumerate(Index, []) when is_integer(Index) -> + []. + %%% Suggestion from OTP-2948: sort and merge with Fun. -spec sort(Fun, List1) -> List2 when diff --git a/lib/stdlib/test/lists_SUITE.erl b/lib/stdlib/test/lists_SUITE.erl index 5a9d72e0e3..fb11cbba8b 100644 --- a/lib/stdlib/test/lists_SUITE.erl +++ b/lib/stdlib/test/lists_SUITE.erl @@ -57,7 +57,8 @@ filter_partition/1, join/1, otp_5939/1, otp_6023/1, otp_6606/1, otp_7230/1, - suffix/1, subtract/1, droplast/1, search/1, hof/1]). + suffix/1, subtract/1, droplast/1, search/1, hof/1, + enumerate/1]). %% Sort randomized lists until stopped. %% @@ -121,7 +122,7 @@ groups() -> {zip, [parallel], [zip_unzip, zip_unzip3, zipwith, zipwith3]}, {misc, [parallel], [reverse, member, dropwhile, takewhile, filter_partition, suffix, subtract, join, - hof, droplast, search]} + hof, droplast, search, enumerate]} ]. init_per_suite(Config) -> @@ -2741,3 +2742,19 @@ hof(Config) when is_list(Config) -> false = lists:all(fun(N) -> N rem 2 =:= 0 end, L), ok. + +%% Test lists:enumerate/1 and lists:enumerate/2 +enumerate(Config) when is_list(Config) -> + [] = lists:enumerate([]), + [] = lists:enumerate(10, []), + [{1,a},{2,b},{3,c}] = lists:enumerate([a,b,c]), + [{10,a},{11,b},{12,c}] = lists:enumerate(10, [a,b,c]), + {'EXIT', {function_clause, _}} = catch lists:enumerate(0), + {'EXIT', {function_clause, _}} = catch lists:enumerate(0, 10), + {'EXIT', {function_clause, _}} = catch lists:enumerate(1.0, []), + {'EXIT', {function_clause, _}} = catch lists:enumerate(1.0, [a,b,c]), + {'EXIT', {function_clause, _}} = catch lists:enumerate(<<1>>, []), + {'EXIT', {function_clause, _}} = catch lists:enumerate(<<1>>, [a,b,c]), + {'EXIT', {function_clause, _}} = catch lists:enumerate(1, <<1,2,3>>), + + ok. -- 2.26.2
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