using C++ boost for each loop

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Hi,

Just playing around with the useful BOOST_FOREACH loop. I have run into a syntax problem

C++

std::vector < std::pair < int, int > > aa;
BOOST_FOREACH(std::pair<int,int>   ptr, aa)
{
              std::cout  << "hello";
}

with the compile errors

C++

ngonl/src/bom/ProActiveOnloadList.cpp:134:56: macro "BOOST_FOREACH" passed 3 arguments, but takes just 2
ngonl/src/bom/ProActiveOnloadList.cpp:134:56: macro "BOOST_FOREACH" passed 3 arguments, but takes just 2
ngonl/src/bom/ProActiveOnloadList.cpp: In function `void <unnamed>::rejectRebateStaff(std::vector<std::pair xmlns:std="#unknown"><com::proactiveonloadpax::segment,>, std::allocator<std::pair><com::proactiveonloadpax::segment,> > >, const COM::PublishedFlightLegDate&)':
ngonl/src/bom/ProActiveOnloadList.cpp: In function `void <unnamed>::rejectRebateStaff(std::vector<std::pair><com::proactiveonloadpax::segment,>, std::allocator<std::pair><com::proactiveonloadpax::segment,> > >, const COM::PublishedFlightLegDate&)':
ngonl/src/bom/ProActiveOnloadList.cpp:135: error: `BOOST_FOREACH' undeclared (first use this function)
ngonl/src/bom/ProActiveOnloadList.cpp:135: error: `BOOST_FOREACH' undeclared (first use this function)
ngonl/src/bom/ProActiveOnloadList.cpp:135: error: (Each undeclared identifier is reported only once for each function it appears in.)
ngonl/src/bom/ProActiveOnloadList.cpp:135: error: (Each undeclared identifier is reported only once for each function it appears in.)
ngonl/src/bom/ProActiveOnloadList.cpp:135: error: expected `;' before '{' token
ngonl/src/bom/ProActiveOnloadList.cpp:135: error: expected `;' before '{' token

</std::pair></std::pair></unnamed></std::pair></std::pair></unnamed>

Why does it think I am passing in 3 arguments and what should the correct syntax be to get my iterator correct?

I know the vector is empty but I just want the syntax right on the BOOST_FOREACH loop.

I should add that if I have

std::vector<std::pair <int, int> >::iterator  anything;

it compiles fine but I think on BOOST_FOREACH you don't include the std::vector bit.

Thank you for any input

Posted 4-Nov-11 1:11am

minkowski

Updated 4-Nov-11 1:53am

v4

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Eugen Podsypalnikov · Answer 1 · 2011-11-04T01:37:00

Solution 1

Just for a syntax test :) :

C++

std::vector < std::pair < int, int > > aa(/*..*/);
BOOST_FOREACH(std::pair < int, int >/*&*/ pair, aa)
{
  std::cout  << "hello";
}

Posted 4-Nov-11 1:37am

Eugen Podsypalnikov

minkowski · Answer 2 · 2011-11-04T04:36:00

I managed to get it to work...

<pre lang="c++">
std::vector<std::pair <int, int> > aa;
// std::vector<std::pair <int, int> >::iterator afasdf;
std::pair < int, int > pp ;
BOOST_FOREACH(pp , aa)
{
std::cout << "hello";
}

</pre>

but I dont know why it works.....

Still I can plod on with my coding.

Paul M Watt · Answer 3 · 2011-11-04T05:29:00

Have you checked out this link on Boost:

boost foreach[^]

Otherwise, in your second entry, the foreach command needs a variable to receive the output from your container, as well as the instance of the container. You have declared a pair<> object pp to be the variable, and accept each value iterated in the vector aa.

If you want to modify the values in your vector, you would need to use a reference, &pp.

using C++ boost for each loop

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