Related
The purpose of the following code is to display the contents of a structure. It is based on this answer.
#include <iostream>
#include <boost/fusion/adapted/struct/adapt_struct.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
#include <boost/fusion/include/for_each.hpp>
#include <boost/mpl/for_each.hpp>
#include <boost/mpl/range_c.hpp>
#include <boost/bind.hpp>
struct Node {
int a = 4;
double b = 2.2;
};
BOOST_FUSION_ADAPT_STRUCT(Node, b)
struct print_visitor {
template <class Index, class C> void operator()(Index, C &c) {
std::cout << boost::fusion::extension::struct_member_name<
C, Index::value>::call() << "="
<< boost::fusion::at<Index>(c) << std::endl;
}
};
template <class C> void print_fields(C &c) {
typedef boost::mpl::range_c<
int, 0, boost::fusion::result_of::size<C>::type::value> range;
boost::mpl::for_each<range>(
boost::bind<void>(print_visitor(), _1, boost::ref(c)));
}
int main() {
Node n;
print_fields(n);
}
The compiler (gcc version 4.8.2) complains:
invalid use of incomplete type ‘struct boost::fusion::result_of::at<Node, mpl_::integral_c<int, 0> >’
typedef typename T::type type;
What is the reason and how can I resolve this?
Here is the complete output of the compiler:
-*- mode: compilation; default-directory: "~/SearchLib/AstarWithPolicies/temp/" -*-
Compilation started at Thu Dec 10 11:54:27
make -k
g++ -Wall -Wextra -Werror -std=c++11 -pedantic -I ~/boost_1_59_0 -I /usr/include/cairomm-1.0/ -I /usr/include/cairo/ -I /usr/include/sigc++-2.0/ -I /usr/lib/x86_64-linux-gnu/sigc++-2.0/include/ -I /usr/include/freetype2/ -g -c temp.cpp
In file included from /home/meir/boost_1_59_0/boost/utility/enable_if.hpp:15:0,
from /home/meir/boost_1_59_0/boost/fusion/support/tag_of.hpp:11,
from /home/meir/boost_1_59_0/boost/fusion/support/category_of.hpp:12,
from /home/meir/boost_1_59_0/boost/fusion/adapted/struct/detail/extension.hpp:14,
from /home/meir/boost_1_59_0/boost/fusion/adapted/struct/adapt_struct.hpp:27,
from temp.cpp:7:
/home/meir/boost_1_59_0/boost/core/enable_if.hpp: In instantiation of ‘struct boost::lazy_disable_if_c<false, boost::fusion::result_of::at<Node, mpl_::integral_c<int, 0> > >’:
/home/meir/boost_1_59_0/boost/core/enable_if.hpp:70:10: required from ‘struct boost::lazy_disable_if<boost::is_const<Node>, boost::fusion::result_of::at<Node, mpl_::integral_c<int, 0> > >’
/home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic_fwd.hpp:102:5: required by substitution of ‘template<class N, class Sequence> constexpr typename boost::lazy_disable_if<boost::is_const<Sequence>, boost::fusion::result_of::at<Sequence, N> >::type boost::fusion::at(Sequence&) [with N = mpl_::integral_c<int, 0>; Sequence = Node]’
temp.cpp:26:48: required from ‘void print_visitor::operator()(Index, C&) [with Index = mpl_::integral_c<int, 0>; C = Node]’
/home/meir/boost_1_59_0/boost/bind/bind.hpp:315:34: required from ‘void boost::_bi::list2<A1, A2>::operator()(boost::_bi::type<void>, F&, A&, int) [with F = print_visitor; A = boost::_bi::list1<mpl_::integral_c<int, 0>&>; A1 = boost::arg<1>; A2 = boost::reference_wrapper<Node>]’
/home/meir/boost_1_59_0/boost/bind/bind.hpp:907:50: required from ‘boost::_bi::bind_t<R, F, L>::result_type boost::_bi::bind_t<R, F, L>::operator()(A1&&) [with A1 = mpl_::integral_c<int, 0>&; R = void; F = print_visitor; L = boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> >; boost::_bi::bind_t<R, F, L>::result_type = void]’
/home/meir/boost_1_59_0/boost/mpl/for_each.hpp:78:25: required from ‘static void boost::mpl::aux::for_each_impl<false>::execute(Iterator*, LastIterator*, TransformFunc*, F) [with Iterator = boost::mpl::r_iter<mpl_::integral_c<int, 0> >; LastIterator = boost::mpl::r_iter<mpl_::integral_c<int, 1> >; TransformFunc = boost::mpl::identity<mpl_::na>; F = boost::_bi::bind_t<void, print_visitor, boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> > >]’
/home/meir/boost_1_59_0/boost/mpl/for_each.hpp:105:97: required from ‘void boost::mpl::for_each(F, Sequence*, TransformOp*) [with Sequence = boost::mpl::range_c<int, 0, 1>; TransformOp = boost::mpl::identity<mpl_::na>; F = boost::_bi::bind_t<void, print_visitor, boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> > >]’
/home/meir/boost_1_59_0/boost/mpl/for_each.hpp:118:48: required from ‘void boost::mpl::for_each(F, Sequence*) [with Sequence = boost::mpl::range_c<int, 0, 1>; F = boost::_bi::bind_t<void, print_visitor, boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> > >]’
temp.cpp:34:62: required from ‘void print_fields(C&) [with C = Node]’
temp.cpp:39:19: required from here
/home/meir/boost_1_59_0/boost/core/enable_if.hpp:63:30: error: invalid use of incomplete type ‘struct boost::fusion::result_of::at<Node, mpl_::integral_c<int, 0> >’
typedef typename T::type type;
^
In file included from /home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic/begin.hpp:14:0,
from /home/meir/boost_1_59_0/boost/fusion/algorithm/iteration/detail/for_each.hpp:11,
from /home/meir/boost_1_59_0/boost/fusion/algorithm/iteration/for_each.hpp:12,
from /home/meir/boost_1_59_0/boost/fusion/include/for_each.hpp:11,
from temp.cpp:9:
/home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic_fwd.hpp:53:16: error: declaration of ‘struct boost::fusion::result_of::at<Node, mpl_::integral_c<int, 0> >’
struct at;
^
temp.cpp: In instantiation of ‘void print_visitor::operator()(Index, C&) [with Index = mpl_::integral_c<int, 0>; C = Node]’:
/home/meir/boost_1_59_0/boost/bind/bind.hpp:315:34: required from ‘void boost::_bi::list2<A1, A2>::operator()(boost::_bi::type<void>, F&, A&, int) [with F = print_visitor; A = boost::_bi::list1<mpl_::integral_c<int, 0>&>; A1 = boost::arg<1>; A2 = boost::reference_wrapper<Node>]’
/home/meir/boost_1_59_0/boost/bind/bind.hpp:907:50: required from ‘boost::_bi::bind_t<R, F, L>::result_type boost::_bi::bind_t<R, F, L>::operator()(A1&&) [with A1 = mpl_::integral_c<int, 0>&; R = void; F = print_visitor; L = boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> >; boost::_bi::bind_t<R, F, L>::result_type = void]’
/home/meir/boost_1_59_0/boost/mpl/for_each.hpp:78:25: required from ‘static void boost::mpl::aux::for_each_impl<false>::execute(Iterator*, LastIterator*, TransformFunc*, F) [with Iterator = boost::mpl::r_iter<mpl_::integral_c<int, 0> >; LastIterator = boost::mpl::r_iter<mpl_::integral_c<int, 1> >; TransformFunc = boost::mpl::identity<mpl_::na>; F = boost::_bi::bind_t<void, print_visitor, boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> > >]’
/home/meir/boost_1_59_0/boost/mpl/for_each.hpp:105:97: required from ‘void boost::mpl::for_each(F, Sequence*, TransformOp*) [with Sequence = boost::mpl::range_c<int, 0, 1>; TransformOp = boost::mpl::identity<mpl_::na>; F = boost::_bi::bind_t<void, print_visitor, boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> > >]’
/home/meir/boost_1_59_0/boost/mpl/for_each.hpp:118:48: required from ‘void boost::mpl::for_each(F, Sequence*) [with Sequence = boost::mpl::range_c<int, 0, 1>; F = boost::_bi::bind_t<void, print_visitor, boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> > >]’
temp.cpp:34:62: required from ‘void print_fields(C&) [with C = Node]’
temp.cpp:39:19: required from here
temp.cpp:26:48: error: no matching function for call to ‘at(Node&)’
<< boost::fusion::at<Index>(c) << std::endl;
^
temp.cpp:26:48: note: candidates are:
In file included from /home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic/begin.hpp:14:0,
from /home/meir/boost_1_59_0/boost/fusion/algorithm/iteration/detail/for_each.hpp:11,
from /home/meir/boost_1_59_0/boost/fusion/algorithm/iteration/for_each.hpp:12,
from /home/meir/boost_1_59_0/boost/fusion/include/for_each.hpp:11,
from temp.cpp:9:
/home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic_fwd.hpp:102:5: note: template<class N, class Sequence> constexpr typename boost::lazy_disable_if<boost::is_const<Sequence>, boost::fusion::result_of::at<Sequence, N> >::type boost::fusion::at(Sequence&)
at(Sequence& seq);
^
/home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic_fwd.hpp:102:5: note: substitution of deduced template arguments resulted in errors seen above
/home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic_fwd.hpp:107:5: note: template<class N, class Sequence> constexpr typename boost::fusion::result_of::at<const Sequence, N>::type boost::fusion::at(const Sequence&)
at(Sequence const& seq);
^
/home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic_fwd.hpp:107:5: note: template argument deduction/substitution failed:
/home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic_fwd.hpp: In substitution of ‘template<class N, class Sequence> constexpr typename boost::fusion::result_of::at<const Sequence, N>::type boost::fusion::at(const Sequence&) [with N = mpl_::integral_c<int, 0>; Sequence = Node]’:
temp.cpp:26:48: required from ‘void print_visitor::operator()(Index, C&) [with Index = mpl_::integral_c<int, 0>; C = Node]’
/home/meir/boost_1_59_0/boost/bind/bind.hpp:315:34: required from ‘void boost::_bi::list2<A1, A2>::operator()(boost::_bi::type<void>, F&, A&, int) [with F = print_visitor; A = boost::_bi::list1<mpl_::integral_c<int, 0>&>; A1 = boost::arg<1>; A2 = boost::reference_wrapper<Node>]’
/home/meir/boost_1_59_0/boost/bind/bind.hpp:907:50: required from ‘boost::_bi::bind_t<R, F, L>::result_type boost::_bi::bind_t<R, F, L>::operator()(A1&&) [with A1 = mpl_::integral_c<int, 0>&; R = void; F = print_visitor; L = boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> >; boost::_bi::bind_t<R, F, L>::result_type = void]’
/home/meir/boost_1_59_0/boost/mpl/for_each.hpp:78:25: required from ‘static void boost::mpl::aux::for_each_impl<false>::execute(Iterator*, LastIterator*, TransformFunc*, F) [with Iterator = boost::mpl::r_iter<mpl_::integral_c<int, 0> >; LastIterator = boost::mpl::r_iter<mpl_::integral_c<int, 1> >; TransformFunc = boost::mpl::identity<mpl_::na>; F = boost::_bi::bind_t<void, print_visitor, boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> > >]’
/home/meir/boost_1_59_0/boost/mpl/for_each.hpp:105:97: required from ‘void boost::mpl::for_each(F, Sequence*, TransformOp*) [with Sequence = boost::mpl::range_c<int, 0, 1>; TransformOp = boost::mpl::identity<mpl_::na>; F = boost::_bi::bind_t<void, print_visitor, boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> > >]’
/home/meir/boost_1_59_0/boost/mpl/for_each.hpp:118:48: required from ‘void boost::mpl::for_each(F, Sequence*) [with Sequence = boost::mpl::range_c<int, 0, 1>; F = boost::_bi::bind_t<void, print_visitor, boost::_bi::list2<boost::arg<1>, boost::reference_wrapper<Node> > >]’
temp.cpp:34:62: required from ‘void print_fields(C&) [with C = Node]’
temp.cpp:39:19: required from here
/home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic_fwd.hpp:107:5: error: invalid use of incomplete type ‘struct boost::fusion::result_of::at<const Node, mpl_::integral_c<int, 0> >’
/home/meir/boost_1_59_0/boost/fusion/sequence/intrinsic_fwd.hpp:53:16: error: declaration of ‘struct boost::fusion::result_of::at<const Node, mpl_::integral_c<int, 0> >’
struct at;
^
make: *** [all] Error 1
Compilation exited abnormally with code 2 at Thu Dec 10 11:54:27
I found this post as I'm practicing the use of the MPL. I got here as I wanted to print the struct_member_name which you were successful at. The short answer is to include <boost/fusion/sequence.hpp>. fusion::at requires a sequence
BOOST_FUSION_ADAPT_STRUCT does only that, it does not create a sequence for the target. If you had have accessed the value in the same way you access the name, it would have worked.
boost::fusion::extension::access::struct_member<C, Index::value>::template apply<C>::call(x)
returns the value of interest. But of course, there is always a better way, that much code is pretty ugly. Once you have a sequence applied to your class, everything gets easier. Now, I didn't find a for_each that iterates and passes types, fusion::for_each dereferences the value and passes that to the functor. So I took some code from boost\fusion\sequence\io\out.hpp which moves across an iterator range.
This example prints the data your way, the iterator way, and directly using fusion's IO. I'm sure I'm missing a whole lot, but this is my first day of actually writing compile time code that works. Thanks for your question, I may not have gotten so far without it!
#include <iostream>
#include <boost/mpl/range_c.hpp>
#include <boost/mpl/for_each.hpp>
#include <boost/fusion/sequence.hpp>
#include <boost/fusion/include/adapt_struct.hpp>
//https://www.boost.org/doc/libs/1_78_0/libs/fusion/doc/html/fusion/support/deduce_sequence.html
#include <boost/bind/bind.hpp>
#include <boost/fusion/iterator/distance.hpp>
struct test {
int val;
std::string name;
};
BOOST_FUSION_ADAPT_STRUCT(test,val,name)
//the origanal with changes
struct print_class
{
template <class Index, typename T>
void operator()(Index, T& x) const
{
std::cout << "from print_class: " << boost::fusion::extension::struct_member_name<T, Index::value>::call()
<< " = " << boost::fusion::at<Index>(x) << std::endl;
}
};
using namespace boost::placeholders;
template <class C> void print_fields(C& c) {
typedef boost::mpl::range_c<
int, 0, boost::fusion::result_of::size<C>::type::value> range;
boost::mpl::for_each<range>(
boost::bind<void>(print_class(), _1, boost::ref(c)));
}
//I could not find anything like this in the fusion namespace, so...
//T is a fusion iterator
namespace boost::fusion {
template <typename T>
auto get_name(){return boost::fusion::extension::struct_member_name<T::seq_type, T::index::value>::call();
}
}
//shamelessly stolen from fusion/io....
namespace {
using namespace boost;
namespace bf = fusion;
struct print_sequence_loop
{
template <typename OS, typename First, typename Last>
static void call(OS&, First&, Last&, mpl::true_)
{
}
template <typename OS, typename First, typename Last>
static void call(OS& os, First& first, Last& last, mpl::false_)
{
bf::result_of::equal_to<
typename bf::result_of::next<First>::type
, Last
>is_last;
//The code that prints
os << bf::get_name<First>() << " = ";
os << *first << std::endl;
//End the code that prints
call(os, fusion::next(first), last, is_last);
}
template <typename OS, typename First, typename Last>
static void call(OS& os, First const& first, Last const& last)
{
bf::result_of::equal_to<First, Last> eq;
call(os, first, last, eq);
}
};
template <typename OS, typename Sequence>
inline void print_sequence(OS& os, Sequence& seq)
{
print_sequence_loop::call(os, fusion::begin(seq), fusion::end(seq));
}
}
using boost::fusion::operators::operator<<;
int main() {
test the_test{ 12,"this is me" };
print_sequence(std::cout, the_test);
std::cout << '\n';
print_fields(the_test);
std::cout << "\n\n this is using fusions OS\n";
std::cout << the_test << std::endl;
}
GCC demo And it works with MSVC.
Why does one variant assignment compile while the other does not? The template instances do not share any types and char could be converted to int, say. What is boost::variant trying to do, that it cannot do in the case of the first assignment and that it can do in the case of the second assignment? Error is below.
#include <string>
#include "boost/variant.hpp"
int main()
{
boost::variant<char> v1;
boost::variant<std::string, int, double> v2;
v1 = v2; // compile error
v2 = v1; // compiles fine
return 0;
}
In file included from /usr/include/boost/variant.hpp:17:0,
from v.cpp:3:
/usr/include/boost/variant/variant.hpp: In instantiation of 'int boost::variant<T0, TN>::convert_copy_into::internal_visit(T&, int) const [with T = const std::basic_string<char>; T0_ = char; TN = {}]':
/usr/include/boost/variant/detail/visitation_impl.hpp:113:9: required from 'typename Visitor::result_type boost::detail::variant::visitation_impl_invoke_impl(int, Visitor&, VoidPtrCV, T*, mpl_::true_) [with Visitor = boost::variant<char>::convert_copy_into; VoidPtrCV = const void*; T = std::basic_string<char>; typename Visitor::result_type = int; mpl_::true_ = mpl_::bool_<true>]'
/usr/include/boost/variant/detail/visitation_impl.hpp:156:9: required from 'typename Visitor::result_type boost::detail::variant::visitation_impl_invoke(int, Visitor&, VoidPtrCV, T*, NoBackupFlag, int) [with Visitor = boost::variant<char>::convert_copy_into; VoidPtrCV = const void*; T = std::basic_string<char>; NoBackupFlag = boost::variant<std::basic_string<char>, int, double>::has_fallback_type_; typename Visitor::result_type = int]'
/usr/include/boost/variant/detail/visitation_impl.hpp:237:5: required from 'typename Visitor::result_type boost::detail::variant::visitation_impl(int, int, Visitor&, VoidPtrCV, mpl_::false_, NoBackupFlag, Which*, step0*) [with Which = mpl_::int_<0>; step0 = boost::detail::variant::visitation_impl_step<boost::mpl::l_iter<boost::mpl::l_item<mpl_::long_<3l>, std::basic_string<char>, boost::mpl::l_item<mpl_::long_<2l>, int, boost::mpl::l_item<mpl_::long_<1l>, double, boost::mpl::l_end> > > >, boost::mpl::l_iter<boost::mpl::l_end> >; Visitor = boost::variant<char>::convert_copy_into; VoidPtrCV = const void*; NoBackupFlag = boost::variant<std::basic_string<char>, int, double>::has_fallback_type_; typename Visitor::result_type = int; mpl_::false_ = mpl_::bool_<false>]'
/usr/include/boost/variant/variant.hpp:2245:13: required from 'static typename Visitor::result_type boost::variant<T0, TN>::internal_apply_visitor_impl(int, int, Visitor&, VoidPtrCV) [with Visitor = boost::variant<char>::convert_copy_into; VoidPtrCV = const void*; T0_ = std::basic_string<char>; TN = {int, double}; typename Visitor::result_type = int]'
/usr/include/boost/variant/variant.hpp:2267:13: [ skipping 2 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/usr/include/boost/variant/variant.hpp:1581:13: required from 'void boost::variant<T0, TN>::convert_construct_variant(Variant&) [with Variant = const boost::variant<std::basic_string<char>, int, double>; T0_ = char; TN = {}]'
/usr/include/boost/variant/variant.hpp:1628:42: required from 'void boost::variant<T0, TN>::convert_construct(const boost::variant<U0, UN ...>&, long int) [with U0 = std::basic_string<char>; UN = {int, double}; T0_ = char; TN = {}]'
/usr/include/boost/variant/variant.hpp:1649:38: required from 'boost::variant<T0, TN>::variant(const T&) [with T = boost::variant<std::basic_string<char>, int, double>; T0_ = char; TN = {}]'
/usr/include/boost/variant/variant.hpp:2059:29: required from 'void boost::variant<T0, TN>::assign(const T&) [with T = boost::variant<std::basic_string<char>, int, double>; T0_ = char; TN = {}]'
/usr/include/boost/variant/variant.hpp:2099:19: required from 'boost::variant<T0, TN>& boost::variant<T0, TN>::operator=(const T&) [with T = boost::variant<std::basic_string<char>, int, double>; T0_ = char; TN = {}]'
v.cpp:10:6: required from here
/usr/include/boost/variant/variant.hpp:1366:61: error: no matching function for call to 'boost::variant<char>::initializer::initialize(void* const&, const std::basic_string<char>&)'
return initializer::initialize(storage_, operand);
^
/usr/include/boost/variant/variant.hpp:1366:61: note: candidates are:
In file included from /usr/include/boost/variant/variant.hpp:32:0,
from /usr/include/boost/variant.hpp:17,
from v.cpp:3:
/usr/include/boost/variant/detail/initializer.hpp:104:24: note: static int boost::detail::variant::make_initializer_node::apply<BaseIndexPair, Iterator>::initializer_node::initialize(void*, boost::detail::variant::make_initializer_node::apply<BaseIndexPair, Iterator>::initializer_node::param_T) [with BaseIndexPair = boost::mpl::pair<boost::detail::variant::initializer_root, mpl_::int_<0> >; Iterator = boost::mpl::l_iter<boost::mpl::list1<char> >; boost::detail::variant::make_initializer_node::apply<BaseIndexPair, Iterator>::initializer_node::param_T = const char&]
static int initialize(void* dest, param_T operand)
^
/usr/include/boost/variant/detail/initializer.hpp:104:24: note: no known conversion for argument 2 from 'const std::basic_string<char>' to 'boost::detail::variant::make_initializer_node::apply<boost::mpl::pair<boost::detail::variant::initializer_root, mpl_::int_<0> >, boost::mpl::l_iter<boost::mpl::list1<char> > >::initializer_node::param_T {aka const char&}'
/usr/include/boost/variant/detail/initializer.hpp:115:24: note: static int boost::detail::variant::make_initializer_node::apply<BaseIndexPair, Iterator>::initializer_node::initialize(void*, boost::detail::variant::make_initializer_node::apply<BaseIndexPair, Iterator>::initializer_node::param2_T) [with BaseIndexPair = boost::mpl::pair<boost::detail::variant::initializer_root, mpl_::int_<0> >; Iterator = boost::mpl::l_iter<boost::mpl::list1<char> >; boost::detail::variant::make_initializer_node::apply<BaseIndexPair, Iterator>::initializer_node::param2_T = char&&]
static int initialize(void* dest, param2_T operand)
^
/usr/include/boost/variant/detail/initializer.hpp:115:24: note: no known conversion for argument 2 from 'const std::basic_string<char>' to 'boost::detail::variant::make_initializer_node::apply<boost::mpl::pair<boost::detail::variant::initializer_root, mpl_::int_<0> >, boost::mpl::l_iter<boost::mpl::list1<char> > >::initializer_node::param2_T {aka char&&}'
/usr/include/boost/variant/detail/initializer.hpp:149:17: note: static void boost::detail::variant::initializer_root::initialize()
static void initialize();
^
/usr/include/boost/variant/detail/initializer.hpp:149:17: note: candidate expects 0 arguments, 2 provided
A char definitely can be stored in an int but the converse is not always true. Therefore the one that fails to compile would be unsafe at runtime, so you're probably better off with it failing. Cast the int to a char if you must.
I'm trying to use mpl_list in for_each
#include <boost/mpl/list.hpp>
#include <algorithm>
#include <boost/mpl/for_each.hpp>
#include <string>
#include <istream>
#include <ostream>
#include <sstream>
#include <iostream>
#include <boost/mpl/range_c.hpp>
#include <boost/mpl/vector.hpp>
#include <boost/mpl/vector_c.hpp>
#include <boost/mpl/at.hpp>
#include <boost/mpl/placeholders.hpp>
#include <boost/bind.hpp>
using namespace std;
namespace mpl = boost::mpl;
typedef mpl::range_c<char,1,5> range5;
typedef mpl::list<
mpl::int_<1>
, mpl::int_<5>
, mpl::int_<31>
, mpl::int_<14>
, mpl::int_<51>
> inp_type;
typedef mpl::list<
mpl::int_<1>
, mpl::int_<5>
, mpl::int_<31>
, mpl::int_<14>
, mpl::int_<51>
> out_type;
template <class T> struct id {};
struct do_this_wrapper {
static char stat_c ;
typedef void result_type;
template<typename U> inline void operator()(int i, U )
{
if (i == U::value)
{
do_this_wrapper::stat_c = mpl::at_c<out_type,U::value>::type::value;
}
}
};
char do_this_wrapper::stat_c ;
int main()
{
int x;
std::cin>>x;
boost::mpl::for_each<inp_type>(boost::bind(do_this_wrapper(), x, _1));
return do_this_wrapper::stat_c;
};
I've got these errors
*... /usr/include/boost/mpl/list/aux_/iterator.hpp: In instantiation of ‘struct boost::mpl::deref >’: /usr/include/boost/mpl/aux_/at_impl.hpp:37:45: required from ‘struct boost::mpl::at_impl::apply, mpl_::int_<5>, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> >, mpl_::long_<5l> >’ /usr/include/boost/mpl/at.hpp:42:8: required from ‘struct boost::mpl::at_c, mpl_::int_<5>, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> >, 5l>’ ../src/TestProj3.cpp:2664:41: required from ‘void do_this_wrapper::operator()(int, U) [with U = mpl_::int_<5>]’ /usr/include/boost/bind/bind.hpp:313:34: required from ‘void boost::_bi::list2::operator()(boost::_bi::type, F&, A&, int) [with F = do_this_wrapper; A = boost::_bi::list1&>; A1 = boost::_bi::value; A2 = boost::arg<1>]’ /usr/include/boost/bind/bind_template.hpp:32:59: required from ‘boost::_bi::bind_t::result_type boost::_bi::bind_t::operator()(A1&) [with A1 = mpl_::int_<5>; R = boost::_bi::unspecified; F = do_this_wrapper; L = boost::_bi::list2, boost::arg<1> >; boost::_bi::bind_t::result_type = void]’ /usr/include/boost/mpl/for_each.hpp:75:25: required from ‘static void boost::mpl::aux::for_each_impl::execute(Iterator*, LastIterator*, TransformFunc*, F) [with Iterator = boost::mpl::l_iter, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> > >; LastIterator = boost::mpl::l_iter; TransformFunc = boost::mpl::identity; F = boost::_bi::bind_t, boost::arg<1> > >]’ /usr/include/boost/mpl/for_each.hpp:79:111: required from ‘static void boost::mpl::aux::for_each_impl::execute(Iterator*, LastIterator*, TransformFunc*, F) [with Iterator = boost::mpl::l_iter, mpl_::int_<5>, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> > >; LastIterator = boost::mpl::l_iter; TransformFunc = boost::mpl::identity; F = boost::_bi::bind_t, boost::arg<1> > >]’ /usr/include/boost/mpl/for_each.hpp:101:97: required from ‘void boost::mpl::for_each(F, Sequence*, TransformOp*) [with Sequence = boost::mpl::list, mpl_::int_<5>, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> >; TransformOp = boost::mpl::identity; F = boost::_bi::bind_t, boost::arg<1> > >]’ /usr/include/boost/mpl/for_each.hpp:111:38: required from ‘void boost::mpl::for_each(F, Sequence*) [with Sequence = boost::mpl::list, mpl_::int_<5>, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> >; F = boost::_bi::bind_t, boost::arg<1> > >]’ ../src/TestProj3.cpp:2678:77: required from here /usr/include/boost/mpl/list/aux_/iterator.hpp:39:33: error: no type named ‘item’ in ‘struct boost::mpl::l_end’ typedef typename Node::item type; ^ /usr/include/boost/mpl/list/aux_/iterator.hpp: In instantiation of ‘struct boost::mpl::next >’: /usr/include/boost/mpl/aux_/preprocessed/gcc/advance_forward.hpp:68:44: required from ‘struct boost::mpl::aux::advance_forward<4l>::apply
/usr/include/boost/mpl/aux_/preprocessed/gcc/apply_wrap.hpp:36:8:
required from ‘struct boost::mpl::apply_wrap1, boost::mpl::l_iter > > >’ /usr/include/boost/mpl/aux_/preprocessed/gcc/advance_forward.hpp:83:21: required from ‘struct boost::mpl::aux::advance_forward<27l>::apply ’ /usr/include/boost/mpl/aux_/preprocessed/gcc/apply_wrap.hpp:36:8:
required from ‘struct boost::mpl::apply_wrap1, boost::mpl::l_iter > > >’ /usr/include/boost/mpl/aux_/preprocessed/gcc/advance_forward.hpp:92:21: required from ‘struct boost::mpl::aux::advance_forward<31l>::apply, mpl_::int_<5>, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> > > >’ /usr/include/boost/mpl/aux_/preprocessed/gcc/apply_wrap.hpp:36:8: [ skipping 7 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ] /usr/include/boost/bind/bind_template.hpp:32:59: required from ‘boost::_bi::bind_t::result_type boost::_bi::bind_t::operator()(A1&) [with A1 = mpl_::int_<31>; R = boost::_bi::unspecified; F = do_this_wrapper; L = boost::_bi::list2, boost::arg<1> >; boost::_bi::bind_t::result_type = void]’ /usr/include/boost/mpl/for_each.hpp:79:111: recursively required from ‘static void boost::mpl::aux::for_each_impl::execute(Iterator*, LastIterator*, TransformFunc*, F) [with Iterator = boost::mpl::l_iter, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> > >; LastIterator = boost::mpl::l_iter; TransformFunc = boost::mpl::identity; F = boost::_bi::bind_t, boost::arg<1> > >]’ /usr/include/boost/mpl/for_each.hpp:79:111: required from ‘static void boost::mpl::aux::for_each_impl::execute(Iterator*, LastIterator*, TransformFunc*, F) [with Iterator = boost::mpl::l_iter, mpl_::int_<5>, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> > >; LastIterator = boost::mpl::l_iter; TransformFunc = boost::mpl::identity; F = boost::_bi::bind_t, boost::arg<1> > >]’ /usr/include/boost/mpl/for_each.hpp:101:97: required from ‘void boost::mpl::for_each(F, Sequence*, TransformOp*) [with Sequence = boost::mpl::list, mpl_::int_<5>, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> >; TransformOp = boost::mpl::identity; F = boost::_bi::bind_t, boost::arg<1> > >]’ /usr/include/boost/mpl/for_each.hpp:111:38: required from ‘void boost::mpl::for_each(F, Sequence*) [with Sequence = boost::mpl::list, mpl_::int_<5>, mpl_::int_<31>, mpl_::int_<14>, mpl_::int_<51> >; F = boost::_bi::bind_t, boost::arg<1> > >]’ ../src/TestProj3.cpp:2678:77: required from here /usr/include/boost/mpl/list/aux_/iterator.hpp:45:43: error: no type named ‘next’ in ‘struct boost::mpl::l_end*’
Would be thankfull for detailed descriprtion or sth to read. Thanks in advance
The issue is
do_this_wrapper::stat_c = mpl::at_c<out_type,U::value>::type::value;
This is asking MPL to find the element at the position in out_type that corresponds to the value of U. Since the inp_type has a value of 51 (among other things), it's failing be able to return the element in position 51 in out_type, since it only contains 5 elements.
Personally, I would attempt to join the two sequences into an associative sequence (mpl::map), and then use for_each over that.
I'm trying to use boost::cregexp_iterator, as exaplined in http://www.boost.org/doc/libs/1_55_0/libs/regex/doc/html/boost_regex/ref/regex_iterator.html
// Loop through all the patterns
auto sessionReconstructionsEnd = _sessionReconstructions.end();
for (auto sr = _sessionReconstructions.begin(); sr != sessionReconstructionsEnd; ++sr) {
const std::string& pattern = sr->first;
const auto& editors = sr->second;
regex re(pattern);
...
for (auto session = sessions.begin(); session != sessionsEnd; ++session) {
for (size_t chunkNumber = 0; chunkNumber < sessionChunks.size(); ++chunkNumber) {
const auto& chunkData = sessionChunks[chunkNumber].data;
cregex_iterator reIteratorEnd;
cregex_iterator reIterator(
reinterpret_cast<const char*>(chunkData.data()),
reinterpret_cast<const char*>(chunkData.data()) + chunkData.size(),
re); // Here the search is being done...
All the other code is commented out. I get the following error:
^
In file included from /usr/include/boost/regex/v4/regex.hpp:67:0,
from /usr/include/boost/regex.hpp:31,
from LGEJobConfiguration.cpp:4:
/usr/include/boost/regex/v4/basic_regex.hpp: In instantiation of ‘boost::basic_regex<charT, traits>::basic_regex(const boost::basic_regex<charT, traits>&) [with charT = char; traits = boost::regex_traits<char>]’:
/usr/include/boost/regex/v4/regex_iterator.hpp:52:43: required from ‘boost::regex_iterator_implementation<BidirectionalIterator, charT, traits>::regex_iterator_implementation(const regex_type*, BidirectionalIterator, boost::regex_constants::match_flag_type) [with BidirectionalIterator = const char*; charT = char; traits = boost::regex_traits<char>; boost::regex_iterator_implementation<BidirectionalIterator, charT, traits>::regex_type = boost::basic_regex<char, boost::regex_traits<char> >; boost::regex_constants::match_flag_type = boost::regex_constants::_match_flags]’
/usr/include/boost/regex/v4/regex_iterator.hpp:113:46: required from ‘boost::regex_iterator<BidirectionalIterator, charT, traits>::regex_iterator(BidirectionalIterator, BidirectionalIterator, const regex_type&, boost::regex_constants::match_flag_type) [with BidirectionalIterator = const char*; charT = char; traits = boost::regex_traits<char>; boost::regex_iterator<BidirectionalIterator, charT, traits>::regex_type = boost::basic_regex<char, boost::regex_traits<char> >; boost::regex_constants::match_flag_type = boost::regex_constants::_match_flags]’
LGEJobConfiguration.cpp:543:8: required from here
/usr/include/boost/regex/v4/basic_regex.hpp:344:29: error: use of deleted function ‘boost::shared_ptr<boost::re_detail::basic_regex_implementation<char, boost::regex_traits<char> > >::shared_ptr(const boost::shared_ptr<boost::re_detail::basic_regex_implementation<char, boost::regex_traits<char> > >&)’
: m_pimpl(that.m_pimpl) {}
^
In file included from /usr/include/boost/shared_ptr.hpp:17:0,
from /usr/include/boost/regex/v4/regex_workaround.hpp:43,
from /usr/include/boost/regex/v4/regex.hpp:32,
from /usr/include/boost/regex.hpp:31,
from LGEJobConfiguration.cpp:4:
/usr/include/boost/smart_ptr/shared_ptr.hpp:168:25: note: ‘boost::shared_ptr<boost::re_detail::basic_regex_implementation<char, boost::regex_traits<char> > >::shared_ptr(const boost::shared_ptr<boost::re_detail::basic_regex_implementation<char, boost::regex_traits<char> > >&)’ is implicitly declared as deleted because ‘boost::shared_ptr<boost::re_detail::basic_regex_implementation<char, boost::regex_traits<char> > >’ declares a move constructor or move assignment operator
template<class T> class shared_ptr
^
/usr/include/boost/smart_ptr/shared_ptr.hpp: In instantiation of ‘boost::shared_ptr<T>& boost::shared_ptr<T>::operator=(const boost::shared_ptr<T>&) [with T = boost::re_detail::named_subexpressions]’:
/usr/include/boost/regex/v4/match_results.hpp:549:20: required from ‘void boost::match_results<BidiIterator, Allocator>::set_named_subs(boost::shared_ptr<boost::re_detail::named_subexpressions>) [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >]’
/usr/include/boost/regex/v4/perl_matcher_common.hpp:265:7: required from ‘bool boost::re_detail::perl_matcher<BidiIterator, Allocator, traits>::find_imp() [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >; traits = boost::regex_traits<char>]’
/usr/include/boost/regex/v4/perl_matcher_common.hpp:230:20: required from ‘bool boost::re_detail::perl_matcher<BidiIterator, Allocator, traits>::find() [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >; traits = boost::regex_traits<char>]’
/usr/include/boost/regex/v4/regex_search.hpp:56:24: required from ‘bool boost::regex_search(BidiIterator, BidiIterator, boost::match_results<Iterator, Allocator>&, const boost::basic_regex<charT, traits>&, boost::regex_constants::match_flag_type, BidiIterator) [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >; charT = char; traits = boost::regex_traits<char>; boost::regex_constants::match_flag_type = boost::regex_constants::_match_flags]’
/usr/include/boost/smart_ptr/shared_ptr.hpp:168:25: note: ‘boost::shared_ptr<boost::re_detail::named_subexpressions>::shared_ptr(const boost::shared_ptr<boost::re_detail::named_subexpressions>&)’ is implicitly declared as deleted because ‘boost::shared_ptr<boost::re_detail::named_subexpressions>’ declares a move constructor or move assignment operator
template<class T> class shared_ptr
^
In file included from /usr/include/boost/regex/v4/regex.hpp:82:0,
from /usr/include/boost/regex.hpp:31,
from LGEJobConfiguration.cpp:4:
/usr/include/boost/regex/v4/match_results.hpp: In instantiation of ‘boost::match_results<BidiIterator, Allocator>::match_results(const boost::match_results<BidiIterator, Allocator>&) [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >]’:
/usr/include/boost/regex/v4/perl_matcher_non_recursive.hpp:134:76: required from ‘boost::re_detail::saved_recursion<Results>::saved_recursion(int, const boost::re_detail::re_syntax_base*, Results*) [with Results = boost::match_results<const char*>]’
/usr/include/boost/regex/v4/perl_matcher_non_recursive.hpp:342:4: required from ‘void boost::re_detail::perl_matcher<BidiIterator, Allocator, traits>::push_recursion(int, const boost::re_detail::re_syntax_base*, boost::re_detail::perl_matcher<BidiIterator, Allocator, traits>::results_type*) [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >; traits = boost::regex_traits<char>; boost::re_detail::perl_matcher<BidiIterator, Allocator, traits>::results_type = boost::match_results<const char*>]’
/usr/include/boost/regex/v4/perl_matcher_non_recursive.hpp:935:127: required from ‘bool boost::re_detail::perl_matcher<BidiIterator, Allocator, traits>::match_endmark() [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >; traits = boost::regex_traits<char>]’
/usr/include/boost/regex/v4/perl_matcher_non_recursive.hpp:147:7: required from ‘bool boost::re_detail::perl_matcher<BidiIterator, Allocator, traits>::match_all_states() [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >; traits = boost::regex_traits<char>]’
/usr/include/boost/regex/v4/perl_matcher_common.hpp:323:21: [ skipping 2 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/usr/include/boost/regex/v4/perl_matcher_common.hpp:230:20: required from ‘bool boost::re_detail::perl_matcher<BidiIterator, Allocator, traits>::find() [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >; traits = boost::regex_traits<char>]’
/usr/include/boost/regex/v4/regex_search.hpp:56:24: required from ‘bool boost::regex_search(BidiIterator, BidiIterator, boost::match_results<Iterator, Allocator>&, const boost::basic_regex<charT, traits>&, boost::regex_constants::match_flag_type, BidiIterator) [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >; charT = char; traits = boost::regex_traits<char>; boost::regex_constants::match_flag_type = boost::regex_constants::_match_flags]’
/usr/include/boost/regex/v4/regex_search.hpp:42:55: required from ‘bool boost::regex_search(BidiIterator, BidiIterator, boost::match_results<Iterator, Allocator>&, const boost::basic_regex<charT, traits>&, boost::regex_constants::match_flag_type) [with BidiIterator = const char*; Allocator = std::allocator<boost::sub_match<const char*> >; charT = char; traits = boost::regex_traits<char>; boost::regex_constants::match_flag_type = boost::regex_constants::_match_flags]’
/usr/include/boost/regex/v4/regex_iterator.hpp:56:54: required from ‘bool boost::regex_iterator_implementation<BidirectionalIterator, charT, traits>::init(BidirectionalIterator) [with BidirectionalIterator = const char*; charT = char; traits = boost::regex_traits<char>]’
/usr/include/boost/regex/v4/regex_iterator.hpp:115:10: required from ‘boost::regex_iterator<BidirectionalIterator, charT, traits>::regex_iterator(BidirectionalIterator, BidirectionalIterator, const regex_type&, boost::regex_constants::match_flag_type) [with BidirectionalIterator = const char*; charT = char; traits = boost::regex_traits<char>; boost::regex_iterator<BidirectionalIterator, charT, traits>::regex_type = boost::basic_regex<char, boost::regex_traits<char> >; boost::regex_constants::match_flag_type = boost::regex_constants::_match_flags]’
LGEJobConfiguration.cpp:543:8: required from here
/usr/include/boost/regex/v4/match_results.hpp:81:130: error: use of deleted function ‘boost::shared_ptr<boost::re_detail::named_subexpressions>::shared_ptr(const boost::shared_ptr<boost::re_detail::named_subexpressions>&)’
: m_subs(m.m_subs), m_named_subs(m.m_named_subs), m_last_closed_paren(m.m_last_closed_paren), m_is_singular(m.m_is_singular)
what the problem?
UPDATE: the problem is with the flag --std=c++11 - I'm posting another post for this issue.
UPDATE2: The problem is I was using an old version of boost (1.4.3), moving to lastest solved it
Let me do your work for you show you how I'd analyze this problem:
#include <boost/regex.hpp>
#include <boost/cregex.hpp>
#include <vector>
int main()
{
using namespace boost;
regex re(".*");
const std::vector<char> chunkData;
cregex_iterator reIteratorEnd;
cregex_iterator reIterator(
reinterpret_cast<const char*>(chunkData.data()),
reinterpret_cast<const char*>(chunkData.data()) + chunkData.size(),
re); // Here the search is being done...}
}
This compiles just fine for me. And there's nothing else given in your question that we can actually reproduce.
You can take it from there. See when it starts to fail. 90% of the time, it will then be obvious why it fails. Otherwise, come back with the clearer, better question.
PS.
I'm aware of the fact that this is technically not an answer. I think it's helping nonetheless (and it doesn't quite fit in a comment)
You of course don't need the re-interpret cast here in my SSCCE. I'm assuming your chunkData might be (who knows) actually a std::deque<unsigned char> or similar? In such a case, see whether you should use a static_cast: When should static_cast, dynamic_cast, const_cast and reinterpret_cast be used? and Regular cast vs. static_cast vs. dynamic_cast
I wanted to write a higher order function filter with C++. The code I have come up with so far is as follows:
#include <iostream>
#include <string>
#include <functional>
#include <algorithm>
#include <vector>
#include <list>
#include <iterator>
using namespace std;
bool isOdd(int const i) {
return i % 2 != 0;
}
template <
template <class, class> class Container,
class Predicate,
class Allocator,
class A
>
Container<A, Allocator> filter(Container<A, Allocator> const & container, Predicate const & pred) {
Container<A, Allocator> filtered(container);
container.erase(remove_if(filtered.begin(), filtered.end(), pred), filtered.end());
return filtered;
}
int main() {
int const a[] = {23, 12, 78, 21, 97, 64};
vector<int const> const v(a, a + 6);
vector<int const> const filtered = filter(v, isOdd);
copy(filtered.begin(), filtered.end(), ostream_iterator<int const>(cout, " "));
}
However on compiling this code, I get the following error messages that I am unable to understand and hence get rid of:
/usr/include/c++/4.3/ext/new_allocator.h: In instantiation of ‘__gnu_cxx::new_allocator<const int>’:
/usr/include/c++/4.3/bits/allocator.h:84: instantiated from ‘std::allocator<const int>’
/usr/include/c++/4.3/bits/stl_vector.h:75: instantiated from ‘std::_Vector_base<const int, std::allocator<const int> >’
/usr/include/c++/4.3/bits/stl_vector.h:176: instantiated from ‘std::vector<const int, std::allocator<const int> >’
Filter.cpp:29: instantiated from here
/usr/include/c++/4.3/ext/new_allocator.h:82: error: ‘const _Tp* __gnu_cxx::new_allocator<_Tp>::address(const _Tp&) const [with _Tp = const int]’ cannot be overloaded
/usr/include/c++/4.3/ext/new_allocator.h:79: error: with ‘_Tp* __gnu_cxx::new_allocator<_Tp>::address(_Tp&) const [with _Tp = const int]’
Filter.cpp: In function ‘Container<A, Allocator> filter(const Container<A, Allocator>&, const Predicate&) [with Container = std::vector, Predicate = bool ()(int), Allocator = std::allocator<const int>, A = const int]’:
Filter.cpp:30: instantiated from here
Filter.cpp:23: error: passing ‘const std::vector<const int, std::allocator<const int> >’ as ‘this’ argument of ‘__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> > std::vector<_Tp, _Alloc>::erase(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, __gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >) [with _Tp = const int, _Alloc = std::allocator<const int>]’ discards qualifiers
/usr/include/c++/4.3/bits/stl_algo.h: In function ‘_FIter std::remove_if(_FIter, _FIter, _Predicate) [with _FIter = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >, _Predicate = bool (*)(int)]’:
Filter.cpp:23: instantiated from ‘Container<A, Allocator> filter(const Container<A, Allocator>&, const Predicate&) [with Container = std::vector, Predicate = bool ()(int), Allocator = std::allocator<const int>, A = const int]’
Filter.cpp:30: instantiated from here
/usr/include/c++/4.3/bits/stl_algo.h:821: error: assignment of read-only location ‘__result.__gnu_cxx::__normal_iterator<_Iterator, _Container>::operator* [with _Iterator = const int*, _Container = std::vector<const int, std::allocator<const int> >]()’
/usr/include/c++/4.3/ext/new_allocator.h: In member function ‘void __gnu_cxx::new_allocator<_Tp>::deallocate(_Tp*, size_t) [with _Tp = const int]’:
/usr/include/c++/4.3/bits/stl_vector.h:150: instantiated from ‘void std::_Vector_base<_Tp, _Alloc>::_M_deallocate(_Tp*, size_t) [with _Tp = const int, _Alloc = std::allocator<const int>]’
/usr/include/c++/4.3/bits/stl_vector.h:136: instantiated from ‘std::_Vector_base<_Tp, _Alloc>::~_Vector_base() [with _Tp = const int, _Alloc = std::allocator<const int>]’
/usr/include/c++/4.3/bits/stl_vector.h:286: instantiated from ‘std::vector<_Tp, _Alloc>::vector(_InputIterator, _InputIterator, const _Alloc&) [with _InputIterator = const int*, _Tp = const int, _Alloc = std::allocator<const int>]’
Filter.cpp:29: instantiated from here
/usr/include/c++/4.3/ext/new_allocator.h:98: error: invalid conversion from ‘const void*’ to ‘void*’
/usr/include/c++/4.3/ext/new_allocator.h:98: error: initializing argument 1 of ‘void operator delete(void*)’
/usr/include/c++/4.3/bits/stl_algobase.h: In function ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false, _II = const int*, _OI = const int*]’:
/usr/include/c++/4.3/bits/stl_algobase.h:435: instantiated from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false, _II = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >, _OI = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >]’
/usr/include/c++/4.3/bits/stl_algobase.h:466: instantiated from ‘_OI std::copy(_II, _II, _OI) [with _II = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >, _OI = __gnu_cxx::__normal_iterator<const int*, std::vector<const int, std::allocator<const int> > >]’
/usr/include/c++/4.3/bits/vector.tcc:136: instantiated from ‘__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> > std::vector<_Tp, _Alloc>::erase(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, __gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >) [with _Tp = const int, _Alloc = std::allocator<const int>]’
Filter.cpp:23: instantiated from ‘Container<A, Allocator> filter(const Container<A, Allocator>&, const Predicate&) [with Container = std::vector, Predicate = bool ()(int), Allocator = std::allocator<const int>, A = const int]’
Filter.cpp:30: instantiated from here
/usr/include/c++/4.3/bits/stl_algobase.h:396: error: no matching function for call to ‘std::__copy_move<false, true, std::random_access_iterator_tag>::__copy_m(const int*&, const int*&, const int*&)’
Please tell me what I am doing wrong here and what is the correct way to achieve the kind of higher order polymorphism I want.
Thanks.
EDIT:
Thank you, everyone. Here's the new code I got after applying your suggestions (and it works now, yay!)
#include <iostream>
#include <string>
#include <functional>
#include <algorithm>
#include <vector>
#include <list>
#include <iterator>
using namespace std;
bool isOdd(int const i) {
return i % 2 != 0;
}
template <
template <typename, typename> class Container,
typename Predicate,
typename Allocator,
typename A
>
Container<A, Allocator> filter(Container<A, Allocator> const & container, Predicate const & pred) {
Container<A, Allocator> filtered(container);
filtered.erase(remove_if(filtered.begin(), filtered.end(), pred), filtered.end());
return filtered;
}
int main() {
int a[] = {23, 12, 78, 21, 97, 64};
vector<int> v(a, a + 6);
vector<int> filtered = filter(v, isOdd);
copy(filtered.begin(), filtered.end(), ostream_iterator<int>(cout, " "));
}
Why is your Container parametrized at all?
template <typename C, typename P>
C filter(C const & container, P pred) {
C filtered(container);
filtered.erase(remove_if(filtered.begin(), filtered.end(), pred), filtered.end());
return filtered;
}
Works just as well. Notice that I passed P by value rather than by const reference, as advised by Meyers in Effective C++ (iterators and functors should be passed by value).
what about remove_copy_if instead ? (with isEven()). It's already built for you.
The error is not in filter, but in:
int main() {
int const a[] = {23, 12, 78, 21, 97, 64};
vector<int const> const v(a, a + 6);
}
You can't have a vector of const stuff. Remove the inner const:
int main() {
int const a[] = {23, 12, 78, 21, 97, 64};
vector<int> const v(a, a + 6);
}
(And of course, filtered.erase, not container.erase.)
container is a const-reference. You can't call erase() on it. You probably mean to call
filtered.erase(remove_if(filtered.begin(), filtered.end(), pred), filtered.end());