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authorLukas Larsson <[email protected]>2017-11-20 10:06:29 +0100
committerLukas Larsson <[email protected]>2017-11-20 10:06:29 +0100
commit7de66cbf895db8650e2b3253d910869c67989b35 (patch)
tree75dce536cf3f69215fcf7311af831c0efef57bc2 /lib/stdlib/doc/src
parentd99803e7625e474dee40f0dfebf2b8092add0336 (diff)
parent10912210641fe7d784c4ba6398c24504200ed339 (diff)
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Merge branch 'lukas/stdlib/maps_iterators/OTP-14012'
* lukas/stdlib/maps_iterators/OTP-14012: erts: Limit size of first iterator for hashmaps Update primary bootstrap Update preloaded modules erts: Remove erts_internal:maps_to_list/2 stdlib: Make io_lib and io_lib_pretty use maps iterator erts: Implement batching maps:iterator erts: Implement maps path iterator erts: Implement map iterator using a stack stdlib: Introduce maps iterator API Conflicts: bootstrap/lib/stdlib/ebin/io_lib.beam bootstrap/lib/stdlib/ebin/io_lib_pretty.beam erts/emulator/beam/bif.tab erts/preloaded/ebin/erlang.beam erts/preloaded/ebin/erts_internal.beam erts/preloaded/ebin/zlib.beam
Diffstat (limited to 'lib/stdlib/doc/src')
-rw-r--r--lib/stdlib/doc/src/maps.xml94
1 files changed, 86 insertions, 8 deletions
diff --git a/lib/stdlib/doc/src/maps.xml b/lib/stdlib/doc/src/maps.xml
index 8c7270816b..987d92989d 100644
--- a/lib/stdlib/doc/src/maps.xml
+++ b/lib/stdlib/doc/src/maps.xml
@@ -33,16 +33,31 @@
<p>This module contains functions for maps processing.</p>
</description>
+ <datatypes>
+ <datatype>
+ <name name="iterator"/>
+ <desc>
+ <p>An iterator representing the key value associations in a map.</p>
+ <p>Created using <seealso marker="#iterator-1"><c>maps:iterator/1</c></seealso>.</p>
+ <p>Consumed by <seealso marker="#next-1"><c>maps:next/1</c></seealso>,
+ <seealso marker="#filter-2"><c>maps:filter/2</c></seealso>,
+ <seealso marker="#fold-3"><c>maps:fold/3</c></seealso> and
+ <seealso marker="#map-2"><c>maps:map/2</c></seealso>.</p>
+ </desc>
+ </datatype>
+ </datatypes>
+
<funcs>
<func>
<name name="filter" arity="2"/>
<fsummary>Select pairs that satisfy a predicate.</fsummary>
<desc>
- <p>Returns a map <c><anno>Map2</anno></c> for which predicate
- <c><anno>Pred</anno></c> holds true in <c><anno>Map1</anno></c>.</p>
+ <p>Returns a map <c><anno>Map</anno></c> for which predicate
+ <c><anno>Pred</anno></c> holds true in <c><anno>MapOrIter</anno></c>.</p>
<p>The call fails with a <c>{badmap,Map}</c> exception if
- <c><anno>Map1</anno></c> is not a map, or with <c>badarg</c> if
- <c><anno>Pred</anno></c> is not a function of arity 2.</p>
+ <c><anno>MapOrIter</anno></c> is not a map or valid iterator,
+ or with <c>badarg</c> if <c><anno>Pred</anno></c> is not a
+ function of arity 2.</p>
<p><em>Example:</em></p>
<code type="none">
> M = #{a => 2, b => 3, c=> 4, "a" => 1, "b" => 2, "c" => 4},
@@ -76,12 +91,16 @@
<fsummary></fsummary>
<desc>
<p>Calls <c>F(K, V, AccIn)</c> for every <c><anno>K</anno></c> to value
- <c><anno>V</anno></c> association in <c><anno>Map</anno></c> in
+ <c><anno>V</anno></c> association in <c><anno>MapOrIter</anno></c> in
any order. Function <c>fun F/3</c> must return a new
accumulator, which is passed to the next successive call.
This function returns the final value of the accumulator. The initial
accumulator value <c><anno>Init</anno></c> is returned if the map is
empty.</p>
+ <p>The call fails with a <c>{badmap,Map}</c> exception if
+ <c><anno>MapOrIter</anno></c> is not a map or valid iterator,
+ or with <c>badarg</c> if <c><anno>Fun</anno></c> is not a
+ function of arity 3.</p>
<p><em>Example:</em></p>
<code type="none">
> Fun = fun(K,V,AccIn) when is_list(K) -> AccIn + V end,
@@ -169,6 +188,32 @@ false</code>
</func>
<func>
+ <name name="iterator" arity="1"/>
+ <fsummary>Create a map iterator.</fsummary>
+ <desc>
+ <p>Returns a map iterator <c><anno>Iterator</anno></c> that can
+ be used by <seealso marker="#next-1"><c>maps:next/1</c></seealso>
+ to traverse the key-value associations in a map. When iterating
+ over a map, the memory usage is guaranteed to be bounded no matter
+ the size of the map.</p>
+ <p>The call fails with a <c>{badmap,Map}</c> exception if
+ <c><anno>Map</anno></c> is not a map.</p>
+ <p><em>Example:</em></p>
+ <code type="none">
+> M = #{ a => 1, b => 2 }.
+#{a => 1,b => 2}
+> I = maps:iterator(M).
+[{a,1},{b,2}]
+> {K1, V1, I2} = maps:next(I).
+{a,1,[{b,2}]}
+> {K2, V2, I3} = maps:next(I2).
+{b,2,[]}
+> maps:next(I3).
+none</code>
+ </desc>
+ </func>
+
+ <func>
<name name="keys" arity="1"/>
<fsummary></fsummary>
<desc>
@@ -188,12 +233,16 @@ false</code>
<name name="map" arity="2"/>
<fsummary></fsummary>
<desc>
- <p>Produces a new map <c><anno>Map2</anno></c> by calling function
+ <p>Produces a new map <c><anno>Map</anno></c> by calling function
<c>fun F(K, V1)</c> for every <c><anno>K</anno></c> to value
- <c><anno>V1</anno></c> association in <c><anno>Map1</anno></c> in
+ <c><anno>V1</anno></c> association in <c><anno>MapOrIter</anno></c> in
any order. Function <c>fun F/2</c> must return value
<c><anno>V2</anno></c> to be associated with key <c><anno>K</anno></c>
- for the new map <c><anno>Map2</anno></c>.</p>
+ for the new map <c><anno>Map</anno></c>.</p>
+ <p>The call fails with a <c>{badmap,Map}</c> exception if
+ <c><anno>MapOrIter</anno></c> is not a map or valid iterator,
+ or with <c>badarg</c> if <c><anno>Fun</anno></c> is not a
+ function of arity 2.</p>
<p><em>Example:</em></p>
<code type="none">
> Fun = fun(K,V1) when is_list(K) -> V1*2 end,
@@ -234,6 +283,35 @@ false</code>
</func>
<func>
+ <name name="next" arity="1"/>
+ <fsummary>Get the next key and value from an iterator.</fsummary>
+ <desc>
+ <p>Returns the next key-value association in
+ <c><anno>Iterator</anno></c> and a new iterator for the
+ remaining associations in the iterator.
+ </p>
+ <p>
+ If there are no more associations in the iterator,
+ <c>none</c> is returned.
+ </p>
+ <p><em>Example:</em></p>
+ <code type="none">
+> Map = #{a => 1, b => 2, c => 3}.
+#{a => 1,b => 2,c => 3}
+> Iter = maps:iterator(Map).
+[{a,1},{b,2},{c,3}]
+> {_, _, Iter1} = maps:next(Iter).
+{a,1,[{b,2},{c,3}]}
+> {_, _, Iter2} = maps:next(Iter1).
+{b,2,[{c,3}]}
+> {_, _, Iter3} = maps:next(Iter2).
+{c,3,[]}
+> maps:next(Iter3).
+none</code>
+ </desc>
+ </func>
+
+ <func>
<name name="put" arity="3"/>
<fsummary></fsummary>
<desc>