[Development] Using lambda in QtConcurrent::map

[Stephen Chu]

I am having problem using lambda in QtConcurrent::map() function. The 
following code:

#include <QtConcurrent>

int foo(int i) { return i+1; }

void moo(QList<int> list)
{
     QtConcurrent::mapped(list, [](int i){ return foo(i); });
}


produces errors below with Clang 3.1. Is lambda supported in map()? Or 
do I need to wrap the lambda in a std::function?

clang++ -c -pipe -mmacosx-version-min=10.6 -arch i386 -stdlib=libc++ 
-std=c++11 -g -gdwarf-2 -Wall -W -fPIE -DQT_PRINTSUPPORT_LIB 
-DQT_WIDGETS_LIB -DQT_CONCURRENT_LIB -DQT_NETWORK_LIB -DQT_GUI_LIB 
-DQT_CORE_LIB -I/Qt/5.0/qtbase/mkspecs/macx-clang-libc++-32 
-I../../Dropbox/Client2012 -I../../Dropbox/Client2012/DataTable 
-I../../Dropbox/Client2012/Tools -I../../Dropbox/Client2012/OUTViewer 
-I../../Dropbox/Client2012/OUTViewer/lcms 
-I../../Dropbox/Client2012/OUTViewer/lcms/lcms2-2.4/include 
-I../../Dropbox/Client2012 -I/Qt/5.0/qtbase/include 
-I/Qt/5.0/qtbase/include/QtPrintSupport 
-I/Qt/5.0/qtbase/include/QtWidgets -I/Qt/5.0/qtbase/include/QtConcurrent 
-I/Qt/5.0/qtbase/include/QtNetwork -I/Qt/5.0/qtbase/include/QtGui 
-I/Qt/5.0/qtbase/include/QtCore -I. 
-I/System/Library/Frameworks/OpenGL.framework/Versions/A/Headers 
-I/System/Library/Frameworks/AGL.framework/Headers -I. 
-F/Qt/5.0/qtbase/lib -o moo.o ../../Dropbox/Client2012/Tools/moo.cpp
In file included from ../../Dropbox/Client2012/Tools/moo.cpp:1:
In file included from /Qt/5.0/qtbase/include/QtConcurrent/QtConcurrent:11:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/qtconcurrentfilter.h:1:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/../../src/concurrent/qtconcurrentfilter.h:49:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/qtconcurrentfilterkernel.h:1:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/../../src/concurrent/qtconcurrentfilterkernel.h:50:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/qtconcurrentmapkernel.h:1:
/Qt/5.0/qtbase/include/QtConcurrent/../../src/concurrent/qtconcurrentmapkernel.h:166:78: 
error: no type named 'result_type' in '<lambda at 
../../Dropbox/Client2012/Tools/moo.cpp:7:29>'
class MappedEachKernel : public IterateKernel<Iterator, typename 
MapFunctor::result_type>
 
~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
/Qt/5.0/qtbase/include/QtConcurrent/../../src/concurrent/qtconcurrentmapkernel.h:214:33: 
note: in instantiation of template class 
'QtConcurrent::MappedEachKernel<QList<int>::const_iterator, <lambda at 
../../Dropbox/Client2012/Tools/moo.cpp:7:29> >' requested here
struct SequenceHolder1 : public Base
                                 ^
/Qt/5.0/qtbase/include/QtConcurrent/../../src/concurrent/qtconcurrentmapkernel.h:238:34: 
note: in instantiation of template class 
'QtConcurrent::SequenceHolder1<QList<int>, 
QtConcurrent::MappedEachKernel<QList<int>::const_iterator, <lambda at 
../../Dropbox/Client2012/Tools/moo.cpp:7:29> >, <lambda at 
../../Dropbox/Client2012/Tools/moo.cpp:7:29> >' requested here
     return startThreadEngine(new SequenceHolderType(sequence, functor));
                                  ^
/Qt/5.0/qtbase/include/QtConcurrent/../../src/concurrent/qtconcurrentmap.h:182:12: 
note: in instantiation of function template specialization 
'QtConcurrent::startMapped<void, QList<int>, <lambda at 
../../Dropbox/Client2012/Tools/moo.cpp:7:29> >' requested here
     return startMapped<typename QtPrivate::MapResultType<void, 
MapFunctor>::ResultType>(sequence, QtPrivate::createFunctionWrapper(map));
            ^
../../Dropbox/Client2012/Tools/moo.cpp:7:2: note: in instantiation of 
function template specialization 'QtConcurrent::mapped<QList<int>, 
<lambda at ../../Dropbox/Client2012/Tools/moo.cpp:7:29> >' requested here
         QtConcurrent::mapped(list, [](int i){ return foo(i); });
         ^
In file included from ../../Dropbox/Client2012/Tools/moo.cpp:1:
In file included from /Qt/5.0/qtbase/include/QtConcurrent/QtConcurrent:11:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/qtconcurrentfilter.h:1:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/../../src/concurrent/qtconcurrentfilter.h:49:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/qtconcurrentfilterkernel.h:1:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/../../src/concurrent/qtconcurrentfilterkernel.h:50:
In file included from 
/Qt/5.0/qtbase/include/QtConcurrent/qtconcurrentmapkernel.h:1:
/Qt/5.0/qtbase/include/QtConcurrent/../../src/concurrent/qtconcurrentmapkernel.h:169:34: 
error: no type named 'result_type' in '<lambda at 
../../Dropbox/Client2012/Tools/moo.cpp:7:29>'
     typedef typename MapFunctor::result_type T;
             ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
2 errors generated.