Boost Graph Library: Verification of ReadWritePropertyMapConcept for std::map fails - c++

Question

For some reason, verification of ReadWritePropertyMapConcept for std::map of vertex descriptors and colors fails:
Live on godbolt
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/graph_traits.hpp>
#include <boost/graph/properties.hpp>
#include <boost/property_map/property_map.hpp>
#include <map>
struct Vertex {};
using graph_type = boost::adjacency_list<boost::vecS, boost::vecS,
boost::bidirectionalS, Vertex>;
using vertex_descriptor = boost::graph_traits<graph_type>::vertex_descriptor;
using map_type = std::map<vertex_descriptor, boost::default_color_type>;
BOOST_CONCEPT_ASSERT(
(boost::ReadWritePropertyMapConcept<map_type, vertex_descriptor>));
with errors:
In file included from /opt/compiler-explorer/libs/boost_1_78_0/boost/graph/adjacency_list.hpp:27,
from <source>:1:
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp: In instantiation of 'struct boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>':
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:32:62: required by substitution of 'template<class Model> boost::concepts::detail::yes boost::concepts::detail::has_constraints_(Model*, boost::concepts::detail::wrap_constraints<Model, (& Model::constraints)>*) [with Model = boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>]'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:42:5: required from 'const bool boost::concepts::not_satisfied<boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >::value'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:45:51: required from 'struct boost::concepts::not_satisfied<boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/general.hpp:72:8: required from 'struct boost::concepts::requirement_<void (*)(boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>)>'
<source>:13:1: required from here
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:203:54: error: no type named 'category' in 'struct boost::property_traits<std::map<long unsigned int, boost::default_color_type> >'
203 | typedef typename property_traits<PMap>::category Category;
| ^~~~~~~~
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp: In instantiation of 'struct boost::ReadablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>':
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:32:62: required by substitution of 'template<class Model> boost::concepts::detail::yes boost::concepts::detail::has_constraints_(Model*, boost::concepts::detail::wrap_constraints<Model, (& Model::constraints)>*) [with Model = boost::ReadablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>]'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:42:5: required from 'const bool boost::concepts::not_satisfied<boost::ReadablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >::value'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:45:51: required from 'struct boost::concepts::not_satisfied<boost::ReadablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/general.hpp:72:8: required from 'struct boost::concepts::requirement_<void (*)(boost::ReadablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>)>'
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:206:7: required from 'void boost::ReadWritePropertyMapConcept<PMap, Key>::constraints() [with PMap = std::map<long unsigned int, boost::default_color_type>; Key = long unsigned int]'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:32:62: required by substitution of 'template<class Model> boost::concepts::detail::yes boost::concepts::detail::has_constraints_(Model*, boost::concepts::detail::wrap_constraints<Model, (& Model::constraints)>*) [with Model = boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>]'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:42:5: required from 'const bool boost::concepts::not_satisfied<boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >::value'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:45:51: required from 'struct boost::concepts::not_satisfied<boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/general.hpp:72:8: required from 'struct boost::concepts::requirement_<void (*)(boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>)>'
<source>:13:1: required from here
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:143:54: error: no type named 'key_type' in 'struct boost::property_traits<std::map<long unsigned int, boost::default_color_type> >'
143 | typedef typename property_traits<PMap>::key_type key_type;
| ^~~~~~~~
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:144:55: error: no type named 'reference' in 'struct boost::property_traits<std::map<long unsigned int, boost::default_color_type> >'
144 | typedef typename property_traits<PMap>::reference reference;
| ^~~~~~~~~
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:145:54: error: no type named 'category' in 'struct boost::property_traits<std::map<long unsigned int, boost::default_color_type> >'
145 | typedef typename property_traits<PMap>::category Category;
| ^~~~~~~~
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:154:48: error: no type named 'value_type' in 'struct boost::property_traits<std::map<long unsigned int, boost::default_color_type> >'
154 | typename property_traits<PMap>::value_type val;
| ^~~
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp: In instantiation of 'struct boost::WritablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>':
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:32:62: required by substitution of 'template<class Model> boost::concepts::detail::yes boost::concepts::detail::has_constraints_(Model*, boost::concepts::detail::wrap_constraints<Model, (& Model::constraints)>*) [with Model = boost::WritablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>]'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:42:5: required from 'const bool boost::concepts::not_satisfied<boost::WritablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >::value'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:45:51: required from 'struct boost::concepts::not_satisfied<boost::WritablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/general.hpp:72:8: required from 'struct boost::concepts::requirement_<void (*)(boost::WritablePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>)>'
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:207:7: required from 'void boost::ReadWritePropertyMapConcept<PMap, Key>::constraints() [with PMap = std::map<long unsigned int, boost::default_color_type>; Key = long unsigned int]'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:32:62: required by substitution of 'template<class Model> boost::concepts::detail::yes boost::concepts::detail::has_constraints_(Model*, boost::concepts::detail::wrap_constraints<Model, (& Model::constraints)>*) [with Model = boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>]'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:42:5: required from 'const bool boost::concepts::not_satisfied<boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >::value'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:45:51: required from 'struct boost::concepts::not_satisfied<boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/general.hpp:72:8: required from 'struct boost::concepts::requirement_<void (*)(boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>)>'
<source>:13:1: required from here
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:176:54: error: no type named 'key_type' in 'struct boost::property_traits<std::map<long unsigned int, boost::default_color_type> >'
176 | typedef typename property_traits<PMap>::key_type key_type;
| ^~~~~~~~
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:177:54: error: no type named 'category' in 'struct boost::property_traits<std::map<long unsigned int, boost::default_color_type> >'
177 | typedef typename property_traits<PMap>::category Category;
| ^~~~~~~~
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:185:48: error: no type named 'value_type' in 'struct boost::property_traits<std::map<long unsigned int, boost::default_color_type> >'
185 | typename property_traits<PMap>::value_type val;
| ^~~
In file included from /opt/compiler-explorer/libs/boost_1_78_0/boost/concept/assert.hpp:35,
from /opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:19,
from /opt/compiler-explorer/libs/boost_1_78_0/boost/graph/adjacency_list.hpp:27,
from <source>:1:
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp: In instantiation of 'void boost::ReadWritePropertyMapConcept<PMap, Key>::constraints() [with PMap = std::map<long unsigned int, boost::default_color_type>; Key = long unsigned int]':
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:32:62: required by substitution of 'template<class Model> boost::concepts::detail::yes boost::concepts::detail::has_constraints_(Model*, boost::concepts::detail::wrap_constraints<Model, (& Model::constraints)>*) [with Model = boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>]'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:42:5: required from 'const bool boost::concepts::not_satisfied<boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >::value'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/has_constraints.hpp:45:51: required from 'struct boost::concepts::not_satisfied<boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int> >'
/opt/compiler-explorer/libs/boost_1_78_0/boost/concept/detail/general.hpp:72:8: required from 'struct boost::concepts::requirement_<void (*)(boost::ReadWritePropertyMapConcept<std::map<long unsigned int, boost::default_color_type>, long unsigned int>)>'
<source>:13:1: required from here
/opt/compiler-explorer/libs/boost_1_78_0/boost/property_map/property_map.hpp:208:7: error: no type named 'category' in 'struct boost::property_traits<std::map<long unsigned int, boost::default_color_type> >'
208 | BOOST_CONCEPT_ASSERT((ConvertibleConcept<Category, ReadWriteTag>));
| ^~~~~~~~~~~~~~~~~~~~
Compiler returned: 1
However, std::map surely has key_type, value_type etc. I have also used it in boost::depth_first_search() as color_map as in this question, and it seemed to work.
On the contrary, when the property map is constructed from adapter, the check passes:
int main() {
graph_type g;
std::vector<boost::default_color_type> colors(num_vertices(g));
auto color_map = boost::make_iterator_property_map(
colors.begin(), get(boost::vertex_index, g));
BOOST_CONCEPT_ASSERT(
(boost::ReadWritePropertyMapConcept<decltype(color_map),
boost::default_color_type>));
}
Why is the concept check failing?

Answer 1

A container doesn't usually satisfy the concept requirements for property maps. Put simply: the map is not a property map. At all.
In principle you need to adapt it. Certainly in the case of this associative property map:
std::map<V, C> colors;
auto color_map = make_assoc_property_map(colors);
Live On Compiler Explorer
#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/breadth_first_search.hpp>
#include <fmt/ranges.h>
using C = boost::default_color_type;
template <> struct fmt::formatter<C> {
auto format(C c, auto& ctx) const { return format_to(ctx.out(), "{}", std::array{"white", "gray", "green", "red", "black"}.at(c)); }
};
struct Vertex {};
using G = boost::adjacency_list<boost::vecS, boost::vecS, boost::bidirectionalS,
Vertex>;
int main() {
using V = G::vertex_descriptor;
std::map<V, C> colors;
auto color_map = make_assoc_property_map(colors);
G g(10);
add_edge(0, 1, g);
add_edge(1, 3, g);
add_edge(1, 4, g);
add_edge(3, 2, g);
add_edge(2, 7, g);
breadth_first_search(g, vertex(0, g), boost::color_map(color_map));
fmt::print("{}\n", fmt::join(colors, "\n"));
}
Prints
(0, black)
(1, black)
(2, black)
(3, black)
(4, black)
(5, white)
(6, white)
(7, black)
(8, white)
(9, white)