Question

我无法在这里找到我做错的事。函数eta完成了我的要求但是当我在循环中使用它时，我得到了附加的错误。

bool eta(map<string, TLorentzVector> map_jets, string jet){
    return(  fabs(map_jets[jet].PseudoRapidity()) > 2.5 );
}

然后

vector<pair<string,double> > jets_pt( vec_jets.size() );

    for( vector<pair<string,double> >::iterator it = jets_pt.begin(); it != jets_pt.end(); ++it)
jets_pt.erase(remove_if(jets_pt.begin(),jets_pt.end(),eta(map_jets,it1->first)),jets_pt.end);

我收到错误

/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h: In function '_OutputIterator std::remove_copy_if(_InputIterator, _InputIterator, _OutputIterator, _Predicate) [with _InputIterator = __gnu_cxx::__normal_iterator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>*, std::vector<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double> > > >, _OutputIterator = __gnu_cxx::__normal_iterator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>*, std::vector<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double> > > >, _Predicate = bool]':
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:1291:   instantiated from '_ForwardIterator std::remove_if(_ForwardIterator, _ForwardIterator, _Predicate) [with _ForwardIterator = __gnu_cxx::__normal_iterator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>*, std::vector<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double> > > >, _Predicate = bool]'
/misc/cdf/gbertoli/hww/Diboson_v20_taus/Ana/src/Functions.cc:25:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:1216: error: '__pred' cannot be used as a function
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h: In function '_RandomAccessIterator std::__find_if(_RandomAccessIterator, _RandomAccessIterator, _Predicate, std::random_access_iterator_tag) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>*, std::vector<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double> > > >, _Predicate = bool]':
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:338:   instantiated from '_InputIterator std::find_if(_InputIterator, _InputIterator, _Predicate) [with _InputIterator = __gnu_cxx::__normal_iterator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>*, std::vector<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double> > > >, _Predicate = bool]'
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:1287:   instantiated from '_ForwardIterator std::remove_if(_ForwardIterator, _ForwardIterator, _Predicate) [with _ForwardIterator = __gnu_cxx::__normal_iterator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>*, std::vector<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double>, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, double> > > >, _Predicate = bool]'
/misc/cdf/gbertoli/hww/Diboson_v20_taus/Ana/src/Functions.cc:25:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:260: error: '__pred' cannot be used as a function
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:264: error: '__pred' cannot be used as a function
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:268: error: '__pred' cannot be used as a function
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:272: error: '__pred' cannot be used as a function
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:280: error: '__pred' cannot be used as a function
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:284: error: '__pred' cannot be used as a function
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:288: error: '__pred' cannot be used as a function
mv: cannot stat `/misc/cdf/gbertoli/hww/Diboson_v20_taus/tmp/Linux2.6-GCC_4_1/Ana/srt_dep_tmp.27294': No such file or directory
gmake[2]: *** [/misc/cdf/gbertoli/hww/Diboson_v20_taus/tmp/Linux2.6-GCC_4_1/Ana/libAna-shared/Functions.o] Error 1
gmake[1]: *** [src.lib] Error 2
gmake: *** [Ana.all] Error 2

Answer 1

首先，remove_if的唯一有效签名将单个函数作为谓词参数：

jets_pt.erase(std::remove_if(jets_pt.begin(), jets_pt.end(), eta),
              jets_pt.end());

这意味着eta必须是一个返回bool的函数，并且正好采用一个参数，其类型是容器的值类型：

bool eta(const std::pair<string, double> & p)
{
   // do something useful with p
}

如果这不符合您的账单，因为您需要在谓词中添加其他状态信息，那么您需要将其设为功能对象：

struct Eta
{
  const std::map<string, TLorentzVector> & map_jets;
  Eta(const std::map<string, TLorentzVector> & m) : map_jets(m) { }
  bool operator()(const std::pair<string, double> & p) const
  {
    std::map<string, TLorentzVector>::const_iterator it = map_jets.find(p->second);
    return it == map_jets.end() ?
                 false          :
                 std::fabs(it->second.PseudoRapidity()) > 2.5;
  }
};

现在您必须将remove_if与Eta的实例一起使用：

jets_pt.erase(std::remove_if(jets_pt.begin(), jets_pt.end(), Eta(map_jets)),
              jets_pt.end());  //                            ^^^^^^^^^^^^^

请注意，您对for循环的使用非常可疑;你应该仔细检查一下。

Answer 2

std::remove_if获取所包含类型的值（bool pred (container::value_type)或适当重载operator()的仿函数）。

对于std::map，您必须按照此处remove_if equivalent for std::map解释的那样。

Answer 3

您将bool（调用eta的结果）传递给remove_if，第三个论点。你需要传递一个谓词：指向a的指针函数接受一个参数并返回可能的东西转换为bool或功能对象。在错误消息中， __pred是你的第三个论点; remove_if在这里调用它 pair<string, double>，并期待一个布尔作为回报。你必须提供可以像这样调用的东西。（你可能想要看看boost::bind。）

而BTW：将map值传递给eta可能不是一个好主意。如果地图很大，它会大大减慢速度。

错误：'__ pit'不能用作函数

3 个答案: