Re: [Boost-users] Inconsistent behavior of fusion::find with vector and adapted struct.

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

#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;

}

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