在下面的代码中,我必须限定 equal()
调用(否则我会得到“对重载函数的不明确调用”),但可以调用不限定的 find()
。有什么区别?
#include <iterator>
#include <vector>
#include <iostream>
using std::vector;
using std::cout;
using std::endl;
// Test whether the elements in two ranges are equal.
// Compares the elements in the range [b,e) with those in the range
// beginning at d, and returns true if all of the elements in both ranges match.
template <class InIter1, class InIter2>
bool equal(InIter1 b, InIter1 e, InIter2 d)
{
cout << "My equal()" << endl;
while (b != e)
if ((*b++) != (*d++))
return false;
return true;
}
// Returns an iterator to the first element in the range [b,e)
// that compares equal to t. If no such element is found, the function returns last.
template <class InIter, class T>
InIter find( InIter b, InIter e, const T& t )
{
cout << "My find()" << endl;
while (b != e) {
if ( *b == t )
return b;
b++;
}
return e;
}
/* "Accelerated C++", ex. 8.2 */
int main()
{
static const int arr[] = {8, 7, 15, 21, 30};
vector<int> vec(arr, arr + sizeof(arr) / sizeof(arr[0]) );
cout << "equal() result: " << ::equal(vec.begin(), vec.end(), vec.rbegin()) << endl;
vector<int>::iterator iter = find(vec.begin(), vec.end(), 21);
if (iter == vec.end())
cout << "did not find()" << endl;
else
cout << "find() result: " << *iter << endl;
return 0;
}
我认为它与参数依赖查找有关(请参阅 this question ),但仍然不明白为什么这两个调用不同。
最佳答案
看来您的标准库实现带来了 std::equal
来自其他一些文件,该文件也没有引入 std::find
(也许它用于 vector 的比较运算符)。如果您包括 <algorithm>
,它们都会被引入,并且两种情况都会含糊不清。
关于c++ - 实现 equal() 和 find(),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20724178/