STL find

[hectorDUQUE]

hi guys,
i have sintax problems using a STL find function :-(

   typedef std::set<string> groupOfFileNames_type;
   typedef std::map<string, groupOfFileNames_type> map_groupFN_type;


   typedef std::vector<string> resultsGroups_type;
   typedef std::map<string, resultsGroups_type> map_completeGroups2resultsGroupsByOrders_type;

   map_groupFN_type completeGroup2groups;
   map_group_type   group2numbers;

    for (map_groupFN_type::const_iterator cur_node = completeGroup2groups.begin(),
        end_node = completeGroup2groups.end(); cur_node != end_node; ++cur_node)
    {

        for (groupOfFileNames_type::const_iterator cur_edge = cur_node->second.begin(),
            end_edge = cur_node->second.end(); cur_edge != end_edge; ++cur_edge)
        {

	
          map_group_type::const_iterator group2numbersIterator;

	  map_group_type::const_iterator group2numbersNode0x = group2numbers.begin();
	  map_group_type::const_iterator group2numbersNodeNx = group2numbers.end();

	  group2numbersIterator = find (group2numbersNode0x, group2numbersNodeNx,  "something");
 
        }//for
    }//for

i am trying to match info between two maps.

the find function (STL searching algorithm) has this message in compilation time:

adResultGroupsFIND.Tpo -c hD_loadResultGroupsFIND.cxx  -fPIC -DPIC -o .libs/hD_loadResultGroupsFIND.o
/usr/lib/gcc/i386-redhat-linux/4.1.1/../../../../include/c++/4.1.1/bits/stl_algo.h: In function '_InputIterator std::__find(_InputIterator, _InputIterator, const _Tp&, std::input_iterator_tag) [with _InputIterator = std::_Rb_tree_const_iterator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::set<int, std::less<int>, std::allocator<int> > > >, _Tp = char [9]]':
/usr/lib/gcc/i386-redhat-linux/4.1.1/../../../../include/c++/4.1.1/bits/stl_algo.h:316:   instantiated from '_InputIterator std::find(_InputIterator, _InputIterator, const _Tp&) [with _InputIterator = std::_Rb_tree_const_iterator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::set<int, std::less<int>, std::allocator<int> > > >, _Tp = char [9]]'
hD_loadResultGroupsFIND.cxx:57:   instantiated from here
/usr/lib/gcc/i386-redhat-linux/4.1.1/../../../../include/c++/4.1.1/bits/stl_algo.h:173: error: no match for 'operator==' in '__first. std::_Rb_tree_const_iterator<_Tp>::operator* [with _Tp = std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::set<int, std::less<int>, std::allocator<int> > >]() == __val'
make[2]: *** [hD_loadResultGroupsFIND.lo] Error 1
make[2]: Leaving directory `/home/duque32/hD_projects/hD_rouletteGambler/map'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/duque32/hD_projects/hD_rouletteGambler'
make: *** [all] Error 2

i wonder if i can use the find STL seaching algortihm with maps?

thanks in advance for help.

hector

 

[cpjust]

Are you trying to find a map key with "something" or map data with "something"?
What does the map_group_type typedef look like?
If you're searching through a map, I think you need to use the find() member of the map class instead of the one in <algorithm>.

 

[hectorDUQUE]

Are you trying to find a map key with "something" or map data with "something"?"
R/ a map key with "something"


"What does the map_group_type typedef look like?"

   typedef std::set<int>    groupOfNumbers_type;
   typedef std::map<string, groupOfNumbers_type> map_group_type;

"If you're searching through a map, I think you need to use the find() member of the map class instead of the one in <algorithm>."

R/ the STL manual (stlfreedoc) says "those algorithms are mostly used on STL containers"
I hope it includes this algortihm for maps :-(

my concern is that i would like to apply a lot of those algorithms to the key or data parts of maps. If not, i have to move info from maps to vectors, before aplying them; isn't it ?

regards,

hector

 

[cpjust]

So why not do this instead:

group2numbersIterator = group2numbers.find( "something" );

It's always better to use the find() & sort() functions that come with STL containers rather than the generic version of those algorithms since the generic functions can't be optimized for use with that type of container.

 

[hectorDUQUE]

thanks cpjust, it works.

what about the map data part?
wit this code:

groupOfNumbers_type::const_iterator groupOfNumbersIterator;
groupOfNumbersIterator = group2numbers->second.find( "28" );

i got:

hD_loadResultGroupsFIND.cxx:69: error: base operand of '->' has non-pointer type 'std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::set<int, std::less<int>, std::allocator<int> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::set<int, std::less<int>, std::allocator<int> > > > >'

hector

 

[cpjust]

The important part of that error is:

base operand of '->' has non-pointer type 'std::map

The rest is just STL type expansion which is too hard to read and irrelevant.
It's telling you that since group2numbers is a regular std::map, not a std::map*, so you can't use -> on it.
Try this instead:

groupOfNumbersIterator = group2numbers.second.find( "28" );

 

[hectorDUQUE]

i've done before:

hD_loadResultGroupsFIND.cxx:70: error: 'class std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::set<int, std::less<int>, std::allocator<int> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::set<int, std::less<int>, std::allocator<int> > > > >' has no member named 'second'

has no member named 'second' :-(

 

[cpjust]

Oops, what was I thinking...
the second field is used with a map iterator, not the map itself. You'll need to replace group2numbers with an iterator to an element of that map. Then change the . back to a ->

 

[hectorDUQUE]

ohh, this stuff is getting me crazy ...

this code works for the map data part:

	    groupOfNumbers_type::const_iterator groupOfNumbersIterator = group2numbersIterator->second.begin();
	    groupOfNumbersIterator = group2numbersIterator->second.find( 28 );

thanks cpjust

hector