[Boost-users] indirect_iterator_generator and std::distance ambiguity

24 Sep 2003

      I'm having problems compiling the code below with boost_1_30_2 and VC71
complaining about:

...\Microsoft Visual Studio .NET 2003\Vc7\include\xutility(489)
: error C2665: 'std::_Distance2'
: none of the 4 overloads can convert parameter 4
from type 'std::iterator_traits<_Iter>::iterator_category'
        with
        [
            _Iter=CDictionary::tVarConstItr
        ]
...

Replacing with std::distance( lBeg.base(), lItr.base() ) does compile and
work properly. Am I missing something in the typedef of tVarConstItr that
would allow direct usage?

----------------------------------------------------------

class CDictionary
{
...

    class VarSpec
    {
        ...
        typedef boost::shared_ptr<VarSpec> tPtr;
    };

typedef VarSpec              tVar;
typedef tVar::tPtr           tVarPtr;
typedef std::vector<tVarPtr> tVars;

typedef boost::indirect_iterator_generator
< tVars::const_iterator
, tVar
, tVar&
, tVar*
, std::iterator_traits<tVars::const_iterator>
::iterator_category
...
::type tVarConstItr;
typedef boost::indirect_iterator_generator
< tVars::iterator
, tVar
, tVar&
, tVar*
, std::iterator_traits<tVars::iterator>
::iterator_category
...
::type tVarItr;
tGroups Groups()const{ return mGroups; }

tVarItr      VarBegin()     { return tVarItr     ( mVars.begin() ); }
tVarItr      VarEnd  ()     { return tVarItr     ( mVars.end  () ); }
tVarConstItr VarBegin()const{ return tVarConstItr( mVars.begin() ); }
tVarConstItr VarEnd  ()const{ return tVarConstItr( mVars.end  () ); }

};

usage:
------
int CDictionaryEditorView::Idx( const  TCHAR* aChrPtr, bool aExact )const
{
   boost::function1<bool,const CDictionary::VarSpec&> lFindFnc;

   if( aExact )
   {
      lFindFnc = boost::bind( std::equal_to<std::string>()
                            , std::string(aChrPtr)
                            , boost::bind( &CDictionary::VarSpec::Name, _1 )
                            );
   }
   else
   {
     //...
   }
   CDictionary::tVarConstItr lBeg = mDctPtr->VarBegin();
   CDictionary::tVarConstItr lEnd = mDctPtr->VarEnd  ();

   CDictionary::tVarConstItr lItr = std::find_if( lBeg, lEnd, lFindFnc );

   return (lItr!=lEnd)? std::distance( lBeg, lItr ) : -1;
}

-- 

Jeff Flinn
Applied Dynamics, International