所以我有下面的简单示例:
#include <iostream>
#include <memory>
#include <vector>
#include <algorithm>
using namespace std;
struct foo
{};
int main(void)
{
vector<shared_ptr<foo>> v;
auto f1 = make_shared<foo>();
auto f2 = make_shared<foo>();
auto f3 = make_shared<foo>();
auto f4 = make_shared<foo>();
v.push_back(f1);
v.push_back(f2);
v.push_back(f3);
v.push_back(f4);
cout << v.size() << endl;
v.erase(remove_if(begin(v), end(v), f2), end(v));
cout << v.size() << endl;
}
为什么此
remove_if
认为f2
是谓词而不是我要查找的值?我真的需要在这里提供谓词才能使它起作用吗?还是我在这里做错了什么?(注意:编译器:gcc 4.8.2 -std = c++ 11)
编辑:应该有rtfm!无论如何-这是编译器的输出:
In file included from /usr/local/gcc/4.8.2/include/c++/4.8/algorithm:62:0,
from remove_if.cpp:4:
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h: In instantiation of '_FIter std::remove_if(_FIter, _FIter, _Predicate) [with _FIter = __gnu_cxx::__normal_iterator<std::shared_ptr<foo>*, std::vector<std::shared_ptr<foo> > >; _Predicate = std::shared_ptr<foo>]':
remove_if.cpp:29:41: required from here
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:1150:33: error: no match for call to '(std::shared_ptr<foo>) (std::shared_ptr<foo>&)'
if(!bool(__pred(*__first)))
^
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h: In instantiation of '_RandomAccessIterator std::__find_if(_RandomAccessIterator, _RandomAccessIterator, _Predicate, std::random_access_iterator_tag) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<std::shared_ptr<foo>*, std::vector<std::shared_ptr<foo> > >; _Predicate = std::shared_ptr<foo>]':
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:4465:41: required from '_IIter std::find_if(_IIter, _IIter, _Predicate) [with _IIter = __gnu_cxx::__normal_iterator<std::shared_ptr<foo>*, std::vector<std::shared_ptr<foo> > >; _Predicate = std::shared_ptr<foo>]'
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:1144:64: required from '_FIter std::remove_if(_FIter, _FIter, _Predicate) [with _FIter = __gnu_cxx::__normal_iterator<std::shared_ptr<foo>*, std::vector<std::shared_ptr<foo> > >; _Predicate = std::shared_ptr<foo>]'
remove_if.cpp:29:41: required from here
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:214:23: error: no match for call to '(std::shared_ptr<foo>) (std::shared_ptr<foo>&)'
if (__pred(*__first))
^
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:218:23: error: no match for call to '(std::shared_ptr<foo>) (std::shared_ptr<foo>&)'
if (__pred(*__first))
^
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:222:23: error: no match for call to '(std::shared_ptr<foo>) (std::shared_ptr<foo>&)'
if (__pred(*__first))
^
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:226:23: error: no match for call to '(std::shared_ptr<foo>) (std::shared_ptr<foo>&)'
if (__pred(*__first))
^
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:234:23: error: no match for call to '(std::shared_ptr<foo>) (std::shared_ptr<foo>&)'
if (__pred(*__first))
^
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:238:23: error: no match for call to '(std::shared_ptr<foo>) (std::shared_ptr<foo>&)'
if (__pred(*__first))
^
/usr/local/gcc/4.8.2/include/c++/4.8/bits/stl_algo.h:242:23: error: no match for call to '(std::shared_ptr<foo>) (std::shared_ptr<foo>&)'
if (__pred(*__first))
最佳答案
因为那是remove_if
所做的;第三个参数是谓词,用于测试是否删除元素。据推测,由于shared_ptr
不能像函数一样被调用,因此您的代码无法编译。
如果要删除具有特定值的元素,请使用 remove
。
关于c++ - 为什么std::remove_if认为shared_ptr <T>是谓词?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/26505553/