Question

在此程序中，出现以下错误：

no match for 'operator<<' (operand types are 'std::ostream {aka std::basic_ostream<char>}' and '__gnu_cxx::__normal_iterator<std::__cxx11::basic_string<char>*, std::vector<std::__cxx11::basic_string<char> > >')

在以下代码中引用cout <<计数。我对C ++很陌生，不确定如何解决此问题。我查看了其他与错误类似的示例，但都没有发现与我有关的示例。如何解决此错误？我猜测它与vector :: size_type和vector.end（）类型自动转换有关，无法计数并且无法转换为char或string，但是我该如何解决？

#include <algorithm>
#include <vector>
#include <iostream>
#include <string>
using namespace std;

ostream &print(ostream &os, const vector<string> &vs)
{
    for(const auto &i: vs)
      os << i << " ";
    return os;
}

string make_plural(size_t ctr, const string &word, const string &ending = "s") {
     return (ctr > 1) ? word + ending : word;
}

// if list used instead, no need for erase since it is default called unique
// member call
void elimDups(vector<string> &words)
{
    sort(words.begin(), words.end());
    auto end_unique = unique(words.begin(), words.end());
    words.erase(end_unique, words.end());
    print(cout, words);
}

void biggies(vector<string> &words, vector<string>::size_type sz)
{
    elimDups(words); // alphabetize words order and remove dups
    // sort words by size and alphabetize same size
    stable_sort(words.begin(), words.end(), 
      [] (const string &a, const string &b)
          { return a.size() < b.size();});
// get an iterator to the first element whose size() is >= sz
    auto wc = find_if(words.begin(), words.end(), [sz] (const string &a)
       { return a.size() >= sz; });
    auto count = words.end() - sz;
    cout << count << " "
         << make_plural(count, "word", "s")
         << " of length " << sz
         << " or longer" << endl;
         // print words of the given size or longer, each one followed by a space
    for_each(wc, words.end(), [] (const string &s)
       { cout << s << " ";});
    cout << endl;
}

int main()
{
    vector<string> vs2{"fox", "the", "jumps", "over", 
      "quick", "red", "slow", "red", "turtle"}

    elimDups(vs);
    elimDups(vs2);

    return 0;
 }

Answer 1

函数void biggies(vector<string> &words, vector<string>::size_type sz)中第38行的语句

auto count = words.end() - sz;

words.end()部分为您提供了一个迭代器，然后您减去了一个标量，它又为您提供了一个迭代器。

因此变量count是一个迭代器，而运算符<<没有为迭代器定义。

您可以做的是：

 auto count = words.size() - sz; // a number;

或

auto count = words.end() - wc; // a number;

与“ operator <<”不匹配（操作数类型为'std :: ostream'

1 个答案: