New subject: Inconsistent behavior of fusion::find with vector and adapted struct.

5 Aug 2009


      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 

#include 

#include 


#include 


#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 V1;


  // Find against non-const V1

  V1 v1(1,2.0);


  BOOST_MPL_ASSERT_NOT((
b::is_same::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
...
::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_samedemo::employee,int::type,bf::result_of::enddemo::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::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::type,bf::result_of::end<const demo::employee>::type> ));


  assert(*bf::find<const int>(const_e1) == 21);

#endif


  return 0;

}

Inconsistent behavior of fusion::find with vector and adapted struct.

Mike Tegtmeyer

Christopher Schmidt

Mike Tegtmeyer

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participants (2)