[Boost-users] Adapters library: using back_insertor with make_transform_iterator

From: Robert Mathews (rmathews_at_[hidden])
Date: 2005-06-30 15:09:51

How does this work?

I'm trying to use the make_transform_iterator to make a writeable output
iterator (looks like it is referred to as a "Writeable LValue" in the
iterator template code), but I can't figure out how to do it.

Here's the example: (I know that I could have used the
make_transform_iterators on the source iterators in this toy example, but
that won't do for my real application)

typedef map<int,string> Map;
typedef vector<int> V1;
typedef vector<string> V2;
string convert(int iValue)
{
 return str(ostringstream() << iValue);
}

int _tmain(int argc, _TCHAR* argv[])
{
 V1 aSourceVector;
 V2 aTargetVector;
 copy(aSourceVector.begin(), aSourceVector.end(),
  make_transform_iterator(back_inserter(aTargetVector), boost::bind(convert,
_1));
}

The compiler (MSVC 7.1.3008) generates a compile errors like at the end of
this message. Anybody know the right way to do this? Can you use an iterator
adaptor as an output iterator, or is this wishful thinking on my part?

Rob.

Compiling...
make_transform_iterator.cpp
d:\scratch\make_transform_iterator\make_transform_iterator.cpp(20) : error
C2514: 'std::basic_ostringstream<_Elem,_Traits,_Alloc>' : class has no
constructors
        with
        [
            _Elem=char,
            _Traits=std::char_traits<char>,
            _Alloc=std::allocator<char>
        ]
        d:\scratch\make_transform_iterator\make_transform_iterator.cpp(20) :
see reference to class template instantiation
'std::basic_ostringstream<_Elem,_Traits,_Alloc>' being compiled
        with
        [
            _Elem=char,
            _Traits=std::char_traits<char>,
            _Alloc=std::allocator<char>
        ]
d:\scratch\make_transform_iterator\make_transform_iterator.cpp(20) : error
C3861: 'str': identifier not found, even with argument-dependent lookup
d:\svn\code\thirdpty\boost\boost_1.32.0\boost\iterator\iterator_facade.hpp(6
52) : error C2182: 'n' : illegal use of type 'void'

d:\svn\code\thirdpty\boost\boost_1.32.0\boost\iterator\iterator_adaptor.hpp(
266) : see reference to class template instantiation
'boost::iterator_facade<Derived,Value,CategoryOrTraversal,Reference,Differen
ce>' being compiled
        with
        [

Derived=boost::transform_iterator<boost::_bi::bind_t<std::string,std::string
(__cdecl
*)(int),boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>>::B1>>,std::ba
ck_insert_iterator<V2>,boost::use_default,boost::use_default>,

Value=boost::mpl::identity<boost::detail::transform_iterator_base<boost::_bi
::bind_t<std::string,std::string (__cdecl
*)(int),boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>>::B1>>,std::ba
ck_insert_iterator<V2>,boost::use_default,boost::use_default>::cv_value_type
>::type,

CategoryOrTraversal=boost::mpl::identity<boost::incrementable_traversal_tag>
::type,

Reference=boost::mpl::identity<boost::detail::transform_iterator_base<boost:
:_bi::bind_t<std::string,std::string (__cdecl
*)(int),boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>>::B1>>,std::ba
ck_insert_iterator<V2>,boost::use_default,boost::use_default>::cv_value_type
>::type,

Difference=boost::iterator_difference<std::back_insert_iterator<V2>>::type
        ]

d:\svn\code\thirdpty\boost\boost_1.32.0\boost\iterator\transform_iterator.hp
p(92) : see reference to class template instantiation
'boost::iterator_adaptor<Derived,Base,Value,Traversal,Reference>' being
compiled
        with
        [

Derived=boost::transform_iterator<boost::_bi::bind_t<std::string,std::string
(__cdecl
*)(int),boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>>::B1>>,std::ba
ck_insert_iterator<V2>,boost::use_default,boost::use_default>,
            Base=std::back_insert_iterator<V2>,

Value=boost::detail::transform_iterator_base<boost::_bi::bind_t<std::string,
std::string (__cdecl
*)(int),boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>>::B1>>,std::ba
ck_insert_iterator<V2>,boost::use_default,boost::use_default>::cv_value_type
,
            Traversal=boost::use_default,

Reference=boost::detail::transform_iterator_base<boost::_bi::bind_t<std::str
ing,std::string (__cdecl
*)(int),boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>>::B1>>,std::ba
ck_insert_iterator<V2>,boost::use_default,boost::use_default>::reference
        ]
        d:\scratch\make_transform_iterator\make_transform_iterator.cpp(28) :
see reference to class template instantiation
'boost::transform_iterator<UnaryFunction,Iterator,Reference,Value>' being
compiled
        with
        [
            UnaryFunction=boost::_bi::bind_t<std::string,std::string
(__cdecl
*)(int),boost::_bi::list1<boost::_bi::list_av_1<boost::arg<1>>::B1>>,
            Iterator=std::back_insert_iterator<V2>,
            Reference=boost::use_default,
            Value=boost::use_default
        ]
d:\svn\code\thirdpty\boost\boost_1.32.0\boost\iterator\iterator_facade.hpp(6
92) : error C2182: 'n' : illegal use of type 'void'
d:\svn\code\thirdpty\boost\boost_1.32.0\boost\iterator\iterator_facade.hpp(6
98) : error C2182: 'n' : illegal use of type 'void'
d:\svn\code\thirdpty\boost\boost_1.32.0\boost\iterator\iterator_facade.hpp(7
04) : error C2182: 'x' : illegal use of type 'void'
d:\svn\code\thirdpty\boost\boost_1.32.0\boost\iterator\iterator_adaptor.hpp(
326) : error C2182: 'n' : illegal use of type 'void'
d:\scratch\make_transform_iterator\make_transform_iterator.cpp(28) : error
C2143: syntax error : missing ')' before ';'

Build log was saved at
"file://d:\scratch\make_transform_iterator\Debug\BuildLog.htm"
make_transform_iterator - 8 error(s), 0 warning(s)