boost::filesystem::recursive_directory_iterator end, begin(directory);
auto num_of_files=std::count_if(begin, end,
std::not1(boost::filesystem::is_directory)));
I am trying to negate the function is_directory on the above directory iterator but am hitting a brick wall. I have tried specifying the template for not1
as bool(*)(const boost::filesystem::path&)
and tried static casting the function both without success.
I know I can resort to a lamdba but this is cleaner if it works.
Thanks
std::not1
needs a function object as its argument. This function object can be obtained with std::ptr_fun
, so this should work:
auto num_of_files=std::count_if(begin, end,
std::not1(std::ptr_fun((bool(*)(const boost::filesystem::path&))boost::filesystem::is_directory)));
(the number of parentheses is probably incorrect). BTW, you need the cast because is_directory
is an overloaded function.
However, since you tag you question c++11, you could use lambdas:
auto num_of_files=std::count_if(begin, end, [](const boost::filesystem::path& p) { return !boost::filesystem::is_directory(p); });
not1 accepts an instance of functor class, which should be an Adaptable Predicate (ie with typedefs for return value etc.), while you are trying to feed it with a function pointer. So you need to wrap it in a functor and ptr_fun might help. Perhaps this would work (assume using namespace std; using namespace boost;):
auto num_of_files=count_if(begin, end, not1(ptr_fun(filesystem::is_directory)));
You need ptr_fun,
this rather elaborate illustration should print 1
three times: (see also http://ideone.com/C5HTR )
#include <functional>
#include <string>
#include <algorithm>
#include <iostream>
bool pred(const std::string& s)
{
return s.size() % 2;
}
int main()
{
std::string data[] = { "hello", "world!" };
std::cout << std::count_if(data, data+2,
pred) << std::endl;
std::cout << std::count_if(data, data+2,
std::ptr_fun(pred) ) << std::endl;
std::cout << std::count_if(data, data+2,
std::not1(std::ptr_fun(pred))) << std::endl;
return 0;
}
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