How can I improve this template to accept lambdas in VS2012 - c++

Question

The following is cute little template that I use often. Simply tells me if the given element is a member of a collection (which itself must be compatible with the find_if template):
// returns true if a given collection contains the given element
// NOTE: This is NOT optimized for associative containers!
template <typename ELEMENT, typename COLLECTION, typename PREDICATE>
bool contains(const COLLECTION & collection, ELEMENT element, PREDICATE predicate)
{
return collection.end() != std::find_if(collection.begin(), collection.end(), boost::bind(predicate, element, _1));
}
I'm finding that VC2012 balks if I try to use a lambda as the predicate:
if (!contains(specs, str, [] (CString pathname, CString pattern) { return AsBool(PathMatchSpec(pathname, pattern)); }))
continue;
VS2012SP1 spits out the following for the above context:
1>c:\users\steve\projects\cimex cad-cam\15.0\3rd party\boost\boost\bind\bind.hpp(69): error C2039: 'result_type' : is not a member of 'CMacroInterpreter::GetDirectoryOf::<lambda_60eac39ee69a5bdc77e08d06d79ae4c4>'
1> c:\users\steve\projects\cimex cad-cam\15.0\cimex application\cimcad\macro directory.cpp(166) : see declaration of 'CMacroInterpreter::GetDirectoryOf::<lambda_60eac39ee69a5bdc77e08d06d79ae4c4>'
1> c:\users\steve\projects\cimex cad-cam\15.0\3rd party\boost\boost\bind\bind_template.hpp(15) : see reference to class template instantiation 'boost::_bi::result_traits<R,F>' being compiled
1> with
1> [
1> R=boost::_bi::unspecified,
1> F=CMacroInterpreter::GetDirectoryOf::<lambda_60eac39ee69a5bdc77e08d06d79ae4c4>
1> ]
1> c:\users\steve\projects\cimex cad-cam\15.0\mfc toolbox\miscellaneous.h(360) : see reference to class template instantiation 'boost::_bi::bind_t<R,F,L>' being compiled
1> with
1> [
1> R=boost::_bi::unspecified,
1> F=CMacroInterpreter::GetDirectoryOf::<lambda_60eac39ee69a5bdc77e08d06d79ae4c4>,
1> L=boost::_bi::list2<boost::_bi::value<CString>,boost::arg<1>>
1> ]
1> c:\users\steve\projects\cimex cad-cam\15.0\cimex application\cimcad\macro directory.cpp(166) : see reference to function template instantiation 'bool contains<CString,substring_container_adapter,CMacroInterpreter::GetDirectoryOf::<lambda_60eac39ee69a5bdc77e08d06d79ae4c4>>(const COLLECTION &,ELEMENT,PREDICATE)' being compiled
1> with
1> [
1> COLLECTION=substring_container_adapter,
1> ELEMENT=CString,
1> PREDICATE=CMacroInterpreter::GetDirectoryOf::<lambda_60eac39ee69a5bdc77e08d06d79ae4c4>
1> ]
I'm unclear on how to coerce things to accept the predicate lambda. Seems that boost is unable to deduce the return type of the lambda. And I'm unclear on what I can do to fix that?
I could define a local std::binary_function derivative functor. Just seems like it would be better to fix contains<> to allow it to handle lambdas directly.

Answer 1

It seems to be an issue with boost::bind. Using std::bind instead, your code builds fine with lambdas in VS2012:
#include <functional>
#include <algorithm>
#include <vector>
template <typename ELEMENT, typename COLLECTION, typename PREDICATE>
bool contains(const COLLECTION & collection, ELEMENT element, PREDICATE predicate)
{
return collection.end() != std::find_if(collection.begin(), collection.end(), std::bind(predicate, element, std::placeholders::_1));
}
std::vector<int> a;
int main()
{
a.push_back(1);
a.push_back(2);
a.push_back(3);
a.push_back(42);
bool c = contains(a, 42, [](int a, int b) { return a == b; });
return 0;
}
The same code builds just fine with g++ as well.

Answer 2

You could always try using another lambda:
template <typename ELEMENT, typename COLLECTION, typename PREDICATE>
bool contains(const COLLECTION & collection, ELEMENT element, PREDICATE predicate)
{
typedef typename COLLECTION::value_type VALUE;
return collection.end() != std::find_if(collection.begin(), collection.end(),
[&]( VALUE const & e ){ return predicate( element, e ); });
}