Inconsistent behavior of fusion::find with vector and adapted struct.
I seem to have found an inconsistency in how fusion::find works with fusion::vector and an adapted struct. Basically, attempting to find a non-const type on a const vector with a non-const member works but requires a const-member find for an adapted struct. (See code below). Is this something that was just overlooked or there a technical reason for this behavior. In any case is there some way to identify a adapted struct in the general case (as apposed to the tag of the specific type) that can be used for a workaround? Thanks in advance, Mike #include <boost/fusion/adapted/struct/adapt_struct.hpp> #include <boost/fusion/container/vector/vector.hpp> #include <boost/fusion/algorithm/query/find.hpp> #include <boost/type_traits.hpp> #include <string> #include <iostream> namespace b = boost; namespace bf = boost::fusion; namespace demo { struct employee { std::string name; int age; }; } // demo::employee is now a Fusion sequence BOOST_FUSION_ADAPT_STRUCT( demo::employee, (std::string, name) (int, age)) int main(void) { typedef bf::vector<int,float> V1; // Find against non-const V1 V1 v1(1,2.0); BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<V1,int>::type,bf::result_of::end<V1>::type> )); assert(*bf::find<int>(v1) == 1); // Find against const V1 const V1 const_v1(3,4.0); BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<const V1,int
::type,bf::result_of::end<const V1>::type> ));
assert(*bf::find<int>(const_v1) == 3); // Find against non-const employee demo::employee e1 = {"Foo",18}; BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<demo::employee,int>::type,bf::result_of::end<demo::employee>::type> )); assert(*bf::find<int>(e1) == 18); // Find against const employee const demo::employee const_e1 = {"Bar",21}; #if 0 BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<constdemo::employee, int>::type,bf::result_of::end<const demo::employee>::type> )); assert(*bf::find<int>(const_e1) == 21); #else // note that the find key is a const int for this to work and is inconsistent with fusion::vector BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<constdemo::employee, const int>::type,bf::result_of::end<const demo::employee>::type> )); assert(*bf::find<const int>(const_e1) == 21); #endif return 0; }
I am pretty sure this is a bug. The cv-ness of a certain fusion type should not be relevant in this particular case. You can identify adapted structs by their fusion::struct_tag - tag. -C. Mike Tegtmeyer schrieb:
I seem to have found an inconsistency in how fusion::find works with fusion::vector and an adapted struct. Basically, attempting to find a non-const type on a const vector with a non-const member works but requires a const-member find for an adapted struct. (See code below). Is this something that was just overlooked or there a technical reason for this behavior. In any case is there some way to identify a adapted struct in the general case (as apposed to the tag of the specific type) that can be used for a workaround?
Thanks in advance, Mike
#include <boost/fusion/adapted/struct/adapt_struct.hpp>
#include <boost/fusion/container/vector/vector.hpp>
#include <boost/fusion/algorithm/query/find.hpp>
#include <boost/type_traits.hpp>
#include <string>
#include <iostream>
namespace b = boost;
namespace bf = boost::fusion;
namespace demo
{
struct employee
{
std::string name;
int age;
};
}
// demo::employee is now a Fusion sequence
BOOST_FUSION_ADAPT_STRUCT(
demo::employee,
(std::string, name)
(int, age))
int main(void)
{
typedef bf::vector<int,float> V1;
// Find against non-const V1
V1 v1(1,2.0);
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<V1,int>::type,bf::result_of::end<V1>::type> ));
assert(*bf::find<int>(v1) == 1);
// Find against const V1
const V1 const_v1(3,4.0);
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<const V1,int>::type,bf::result_of::end<const V1>::type> ));
assert(*bf::find<int>(const_v1) == 3);
// Find against non-const employee
demo::employee e1 = {"Foo",18};
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<demo::employee,int>::type,bf::result_of::end<demo::employee>::type> ));
assert(*bf::find<int>(e1) == 18);
// Find against const employee
const demo::employee const_e1 = {"Bar",21};
#if 0
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<const demo::employee,int>::type,bf::result_of::end<const demo::employee>::type> ));
assert(*bf::find<int>(const_e1) == 21);
#else
// note that the find key is a const int for this to work and is inconsistent with fusion::vector
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<const demo::employee,const int>::type,bf::result_of::end<const demo::employee>::type> ));
assert(*bf::find<const int>(const_e1) == 21);
#endif
return 0;
}
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Thanks, added ticket 3322 Mike On Wed, Aug 5, 2009 at 11:47 PM, Christopher Schmidt < mr.chr.schmidt@online.de> wrote:
I am pretty sure this is a bug. The cv-ness of a certain fusion type should not be relevant in this particular case.
You can identify adapted structs by their fusion::struct_tag - tag.
-C.
Mike Tegtmeyer schrieb:
I seem to have found an inconsistency in how fusion::find works with fusion::vector and an adapted struct. Basically, attempting to find a non-const type on a const vector with a non-const member works but requires a const-member find for an adapted struct. (See code below). Is this something that was just overlooked or there a technical reason for this behavior. In any case is there some way to identify a adapted struct in the general case (as apposed to the tag of the specific type) that can be used for a workaround?
Thanks in advance, Mike
#include <boost/fusion/adapted/struct/adapt_struct.hpp>
#include <boost/fusion/container/vector/vector.hpp>
#include <boost/fusion/algorithm/query/find.hpp>
#include <boost/type_traits.hpp>
#include <string>
#include <iostream>
namespace b = boost;
namespace bf = boost::fusion;
namespace demo
{
struct employee
{
std::string name;
int age;
};
}
// demo::employee is now a Fusion sequence
BOOST_FUSION_ADAPT_STRUCT(
demo::employee,
(std::string, name)
(int, age))
int main(void)
{
typedef bf::vector<int,float> V1;
// Find against non-const V1
V1 v1(1,2.0);
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<V1,int>::type,bf::result_of::end<V1>::type> ));
assert(*bf::find<int>(v1) == 1);
// Find against const V1
const V1 const_v1(3,4.0);
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<const V1,int>::type,bf::result_of::end<const V1>::type> ));
assert(*bf::find<int>(const_v1) == 3);
// Find against non-const employee
demo::employee e1 = {"Foo",18};
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<demo::employee,int>::type,bf::result_of::end<demo::employee>::type> ));
assert(*bf::find<int>(e1) == 18);
// Find against const employee
const demo::employee const_e1 = {"Bar",21};
#if 0
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<const demo::employee,int>::type,bf::result_of::end<const demo::employee>::type> ));
assert(*bf::find<int>(const_e1) == 21);
#else
// note that the find key is a const int for this to work and is inconsistent with fusion::vector
BOOST_MPL_ASSERT_NOT(( b::is_same<bf::result_of::find<const demo::employee,const int>::type,bf::result_of::end<const demo::employee>::type> ));
assert(*bf::find<const int>(const_e1) == 21);
#endif
return 0;
}
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participants (2)
-
Christopher Schmidt -
Mike Tegtmeyer