I would like to use Boost Phoenix to generate a lambda function for use in a std::find_if operation on a structure that contains reference-type members. A contrived example is as follow开发者_运维问答s:
struct MyStruct
{
MyStruct() : x(0) {}
int& x;
};
std::vector<MyStruct> AllStructs;
// Search the array for an element for which x == 5
const std::vector<MyStruct>::const_iterator& it =
find_if(
AllStructs.begin(),
AllStructs.end(),
bind(&MyStruct::x, arg1) == 5
);
If MyStruct::x is of type int instead of int&, it compiles fine. But with the reference member I get a "pointer to reference member is illegal" error.
From poking around on the net, it seems like I need to use Phoenix's 'ref' functionality, but I can't seem to figure out the required syntax.
Does anyone know how to get this to work for type 'int&' ?
Sorry that this is far too late, but for future reference, you can use a member pointer:
std::vector<MyStruct>::const_iterator it =
find_if(AllStructs.begin(), AllStructs.end(),
(&boost::phoenix::arg_names::arg1)->*&MyStruct::x == 5
);
You cannot create a pointer to a reference member, just as you cannot create a pointer to a reference. The answer from Daniel James could work only if x was a plain int, rather than int&. See phoenix.modules.operator.member_pointer_operator also.
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