我不明白我在最后一行遇到的编译器错误:
#include <iostream>
#include <algorithm>
struct X{
int number;
};
bool same_number_X(const int & a, const X & b)
{ return a == b.number; }
bool same_number_int(const int & a, const int & b)
{ return a == b; }
int main(){
std::vector<int> vec1{1,2,3};
std::vector<int> vec2{2,3,1};
std::vector<X> vec3{{2},{3},{1}};
std::cout << std::is_permutation(vec1.begin(), vec1.end(), vec2.begin(), same_number_int);
std::cout << std::is_permutation(vec1.begin(), vec1.end(), vec3.begin(), same_number_X);
}
可以看到错误HERE 它说
In instantiation of 'typename std::iterator_traits<_InputIterator>::difference_type std::count_if(_IIter, _IIter, _Predicate) [with _IIter = __gnu_cxx::__normal_iterator<X*, std::vector<X> >; _Predicate = std::_Bind<bool (*(std::_Placeholder<1>, int))(const int&, const X&)>; typename std::iterator_traits<_InputIterator>::difference_type = long int]':
c++/4.7/bits/stl_algo.h:4367:37: required from 'bool std::is_permutation(_FIter1, _FIter1, _FIter2, _BinaryPredicate) [with _FIter1 = __gnu_cxx::__normal_iterator<int*, std::vector<int> >; _FIter2 = __gnu_cxx::__normal_iterator<X*, std::vector<X> >; _BinaryPredicate = bool (*)(const int&, const X&)]'
source.cpp:23:90: required from here
c++/4.7/bits/stl_algo.h:4681:2: error: no match for call to '(std::_Bind<bool (*(std::_Placeholder<1>, int))(const int&, const X&)>) (X&)'
任何人都可以用非编译器语言解释/解决它吗? :-)
最佳答案
来自 C++11 标准的第 25.2.12/1 段:
template<class ForwardIterator1, class ForwardIterator2>
bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2);
template<class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, BinaryPredicate pred);
1 Requires:
ForwardIterator1
andForwardIterator2
shall have the same value type. The comparison function shall be an equivalence relation.
在您上次调用 is_permutation()
时,第一个参数(从中推导出 ForwardIterator1
类型)是 int
值的迭代器,而第三个参数(从中推导出 ForwardIterator2
类型)是 X
值的迭代器。因此,您违反了上一段所述的先决条件。
关于c++ - is_permutation 的编译器错误和结构的谓词,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/15209006/