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authorVille Voutilainen <ville.voutilainen@qt.io>2017-12-05 16:31:53 +0200
committerVille Voutilainen <ville.voutilainen@qt.io>2017-12-08 04:43:38 +0000
commit9856f869f5cd4b7651c10b71b824aff4c006cf3b (patch)
treea93ca898f46ae27f452aa1f195d73f50341c1b6a /src/concurrent/qtconcurrentfilter.cpp
parent216b68083053584497ddf29569ef386c1fa04045 (diff)
Fix documentation for function objects with map/reduce
The documentation claims that function objects just work with map-reduce. They work for the map function, but not for the reduce function. Making them work for the reduce function was deemed too complex for questionable benefit, so this patch explains the situation and provides a work-around. Task-number: QTBUG-22710 Change-Id: I7f706468e36031bc261234310d331001b96e5137 Reviewed-by: Venugopal Shivashankar <Venugopal.Shivashankar@qt.io> Reviewed-by: Nico Vertriest <nico.vertriest@qt.io> Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Diffstat (limited to 'src/concurrent/qtconcurrentfilter.cpp')
-rw-r--r--src/concurrent/qtconcurrentfilter.cpp9
1 files changed, 8 insertions, 1 deletions
diff --git a/src/concurrent/qtconcurrentfilter.cpp b/src/concurrent/qtconcurrentfilter.cpp
index 3e3ed7cf68..d4e4656127 100644
--- a/src/concurrent/qtconcurrentfilter.cpp
+++ b/src/concurrent/qtconcurrentfilter.cpp
@@ -142,12 +142,19 @@
\section2 Using Function Objects
QtConcurrent::filter(), QtConcurrent::filtered(), and
- QtConcurrent::filteredReduced() accept function objects, which can be used to
+ QtConcurrent::filteredReduced() accept function objects
+ for the filter function. These function objects can be used to
add state to a function call. The result_type typedef must define the
result type of the function call operator:
\snippet code/src_concurrent_qtconcurrentfilter.cpp 13
+ For the reduce function, function objects are not directly
+ supported. Function objects can, however, be used
+ when the type of the reduction result is explicitly specified:
+
+ \snippet code/src_concurrent_qtconcurrentfilter.cpp 14
+
\section2 Wrapping Functions that Take Multiple Arguments
If you want to use a filter function takes more than one argument, you can