File 5731-Add-lists-enumerate-3.patch of Package erlang

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File 5731-Add-lists-enumerate-3.patch of Package erlang (Revision c7414e24ac115dc7954a556db05458e9)

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From 54456030a9a1bea26786d8eb888061951111a413 Mon Sep 17 00:00:00 2001
From: Maria Scott <maria-12648430@hnc-agency.org>
Date: Wed, 1 Mar 2023 07:45:02 +0100
Subject: [PATCH] Add lists:enumerate/3

---
 lib/stdlib/doc/src/lists.xml                  | 42 +++++++------------
 lib/stdlib/src/lists.erl                      | 25 +++++++----
 lib/stdlib/test/lists_SUITE.erl               | 24 +++++++++++
 lib/stdlib/test/lists_property_test_SUITE.erl |  4 ++
 lib/stdlib/test/property_test/lists_prop.erl  | 22 ++++++++++
 5 files changed, 83 insertions(+), 34 deletions(-)

diff --git a/lib/stdlib/doc/src/lists.xml b/lib/stdlib/doc/src/lists.xml
index 00caf89d23..f6f329bf85 100644
--- a/lib/stdlib/doc/src/lists.xml
+++ b/lib/stdlib/doc/src/lists.xml
@@ -176,43 +176,33 @@
 
     <func>
       <name name="enumerate" arity="1" since="OTP 25.0"/>
+      <name name="enumerate" arity="2" since="OTP 25.0"/>
+      <name name="enumerate" arity="3" since="OTP 26.0"/>
       <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>
+          <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 <c><anno>Step</anno></c>
+          in each step.</p>
+        <p>That is, <c>enumerate/3</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),
+enumerate(I, S, List) ->
+  {List1, _ } = lists:mapfoldl(fun(T, Acc) -> {{Acc, T}, Acc+S} end, I, List),
   List1.</code>
-        <p><em>Example:</em></p>
+        <p>The default values for <c><anno>Index</anno></c> and
+	  <c><anno>Step</anno></c> are both <c>1</c>.</p>
+        <p><em>Examples:</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>
+        <pre>
+> <input>lists:enumerate(0, -2, [a,b,c]).</input>
+[{0,a},{-2,b},{-4,c}]</pre>
       </desc>
     </func>
     
diff --git a/lib/stdlib/src/lists.erl b/lib/stdlib/src/lists.erl
index b1be8e1c2d..15bed9e292 100644
--- a/lib/stdlib/src/lists.erl
+++ b/lib/stdlib/src/lists.erl
@@ -29,7 +29,7 @@
 %% arguments. Please keep in alphabetical order.
 -export([append/1, append/2, concat/1,
          delete/2, droplast/1, duplicate/2,
-         enumerate/1, enumerate/2,
+         enumerate/1, enumerate/2, enumerate/3,
          flatlength/1, flatten/1, flatten/2,
          join/2, last/1, min/1, max/1,
          nth/2, nthtail/2,
@@ -1160,20 +1160,29 @@ keymap(Fun, Index, []) when is_integer(Index), Index >= 1,
       List2 :: [{Index, T}],
       Index :: integer(),
       T :: term().
-enumerate(List1) when is_list(List1) ->
-    enumerate_1(1, List1).
+enumerate(List1) ->
+    enumerate(1, 1, List1).
 
 -spec enumerate(Index, List1) -> List2 when
       List1 :: [T],
       List2 :: [{Index, T}],
       Index :: integer(),
       T :: term().
-enumerate(Index, List1) when is_integer(Index), is_list(List1) ->
-    enumerate_1(Index, List1).
+enumerate(Index, List1) ->
+    enumerate(Index, 1, List1).
 
-enumerate_1(Index, [H|T]) ->
-    [{Index, H}|enumerate_1(Index + 1, T)];
-enumerate_1(_Index, []) ->
+-spec enumerate(Index, Step, List1) -> List2 when
+      List1 :: [T],
+      List2 :: [{Index, T}],
+      Index :: integer(),
+      Step :: integer(),
+      T :: term().
+enumerate(Index, Step, List1) when is_integer(Index), is_integer(Step) ->
+    enumerate_1(Index, Step, List1).
+
+enumerate_1(Index, Step, [H|T]) ->
+    [{Index, H}|enumerate_1(Index + Step, Step, T)];
+enumerate_1(_Index, _Step, []) ->
     [].
 
 %%% Suggestion from OTP-2948: sort and merge with Fun.
diff --git a/lib/stdlib/test/lists_SUITE.erl b/lib/stdlib/test/lists_SUITE.erl
index 792a94702a..1ab4458a5a 100644
--- a/lib/stdlib/test/lists_SUITE.erl
+++ b/lib/stdlib/test/lists_SUITE.erl
@@ -3198,15 +3198,39 @@ hof(Config) when is_list(Config) ->
 enumerate(Config) when is_list(Config) ->
     [] = lists:enumerate([]),
     [] = lists:enumerate(10, []),
+    [] = lists:enumerate(-10, []),
+    [] = lists:enumerate(10, 2, []),
+    [] = lists:enumerate(10, -2, []),
+    [] = lists:enumerate(-10, 2, []),
+    [] = lists:enumerate(-10, -2, []),
     [{1,a},{2,b},{3,c}] = lists:enumerate([a,b,c]),
     [{10,a},{11,b},{12,c}] = lists:enumerate(10, [a,b,c]),
+    [{-10,a},{-9,b},{-8,c}] = lists:enumerate(-10, [a,b,c]),
+    [{10,a},{12,b},{14,c}] = lists:enumerate(10, 2, [a,b,c]),
+    [{10,a},{8,b},{6,c}] = lists:enumerate(10, -2, [a,b,c]),
+    [{-10,a},{-12,b},{-14,c}] = lists:enumerate(-10, -2, [a,b,c]),
     {'EXIT', {function_clause, _}} = catch lists:enumerate(0),
     {'EXIT', {function_clause, _}} = catch lists:enumerate(0, 10),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(0, 10, 20),
     {'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(1.0, 2, []),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(1.0, 2, [a,b,c]),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(1, 2.0, []),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(1, 2.0, [a,b,c]),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(1.0, 2.0, []),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(1.0, 2.0, [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>>, 2, []),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(<<1>>, 2, [a,b,c]),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(1, <<2>>, []),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(1, <<2>>, [a,b,c]),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(<<1>>, <<2>>, []),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(<<1>>, <<2>>, [a,b,c]),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(<<1,2,3>>),
     {'EXIT', {function_clause, _}} = catch lists:enumerate(1, <<1,2,3>>),
+    {'EXIT', {function_clause, _}} = catch lists:enumerate(1, 2, <<1,2,3>>),
 
     ok.
 
diff --git a/lib/stdlib/test/lists_property_test_SUITE.erl b/lib/stdlib/test/lists_property_test_SUITE.erl
index 4b366d730a..ecbf14309e 100644
--- a/lib/stdlib/test/lists_property_test_SUITE.erl
+++ b/lib/stdlib/test/lists_property_test_SUITE.erl
@@ -35,6 +35,7 @@ all() ->
         duplicate_case,
         enumerate_1_case,
         enumerate_2_case,
+        enumerate_3_case,
         filter_case,
         filtermap_case,
         flatlength_case,
@@ -159,6 +160,9 @@ enumerate_1_case(Config) ->
 enumerate_2_case(Config) ->
     do_proptest(prop_enumerate_2, Config).
 
+enumerate_3_case(Config) ->
+    do_proptest(prop_enumerate_3, Config).
+
 filter_case(Config) ->
     do_proptest(prop_filter, Config).
 
diff --git a/lib/stdlib/test/property_test/lists_prop.erl b/lib/stdlib/test/property_test/lists_prop.erl
index 00b518ff83..68c087b76d 100644
--- a/lib/stdlib/test/property_test/lists_prop.erl
+++ b/lib/stdlib/test/property_test/lists_prop.erl
@@ -240,6 +240,28 @@ prop_enumerate_2() ->
         lists:enumerate(StartIndex, InList) =:= ExpList
     ).
 
+%% enumerate/3
+prop_enumerate_3() ->
+    ?FORALL(
+        {StartIndex, Step, InList, ExpList},
+        ?LET(
+	    {N, S},
+	    {integer(), integer()},
+            ?LET(
+                {L, {_, EL}},
+                gen_list_fold(
+                    gen_any(),
+                    fun(T, {I, Acc}) ->
+                        {I + S, Acc ++ [{I, T}]}
+                    end,
+                    {N, []}
+                ),
+                {N, S, L, EL}
+            )
+        ),
+        lists:enumerate(StartIndex, Step, InList) =:= ExpList
+    ).
+
 %% filter/2
 prop_filter() ->
     ?FORALL(
-- 
2.35.3

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File 5731-Add-lists-enumerate-3.patch of Package erlang (Revision c7414e24ac115dc7954a556db05458e9)

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