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-rw-r--r--lib/stdlib/doc/src/lists.xml25
1 files changed, 25 insertions, 0 deletions
diff --git a/lib/stdlib/doc/src/lists.xml b/lib/stdlib/doc/src/lists.xml
index b6c0fa4e05..1aff78f4fc 100644
--- a/lib/stdlib/doc/src/lists.xml
+++ b/lib/stdlib/doc/src/lists.xml
@@ -152,6 +152,31 @@
</desc>
</func>
<func>
+ <name name="filtermap" arity="2"/>
+ <fsummary>Filter and map elements which satisfy a function</fsummary>
+ <desc>
+ <p>Calls <c><anno>Fun</anno>(<anno>Elem</anno>)</c> on successive elements <c>Elem</c>
+ of <c><anno>List1</anno></c>. <c><anno>Fun</anno>/2</c> must return either a boolean
+ or a tuple <c>{true, <anno>Value</anno>}</c>. The function returns the list of elements
+ for which <c><anno>Fun</anno></c> returns a new value, where a value of <c>true</c>
+ is synonymous with <c>{true, <anno>Elem</anno>}</c>.</p>
+ <p>That is, <c>filtermap</c> behaves as if it had been defined as follows:</p>
+ <code type="none">
+filtermap(Fun, List1) ->
+ lists:foldr(fun(Elem, Acc) ->
+ case Fun(Elem) of
+ false -> Acc;
+ true -> [Elem|Acc];
+ {true,Value} -> [Value|Acc]
+ end,
+ end, [], List1).</code>
+ <p>Example:</p>
+ <pre>
+> <input>lists:filtermap(fun(X) -> case X rem 2 of 0 -> {true, X div 2}; _ -> false end end, [1,2,3,4,5]).</input>
+[1,2]</pre>
+ </desc>
+ </func>
+ <func>
<name name="flatlength" arity="1"/>
<fsummary>Length of flattened deep list</fsummary>
<desc>