新人求指导 c++primer书中例子

Question

P190例子

#include
#include
using namespace std;
string::size_type find_char(const string &s, char c, string::size_type &occurs)
{
auto ret = s.size();
occurs = 0;
for (decltype(ret)i = 0; i != s.size(); ++i){
if (s[i] == c){
if (ret == s.size())
ret = i;
++occurs;
}
}
return ret;
}
int main(){
string a("ewusruywsoieuyruwaufbnsdbyfeywaryawiuruaiwhruwhfadsfsf");
char b = 's';
string::size_type m = 0;
cout << find_char(a, b, m) << '\n'<< m << endl;

return 0;

}

这里m输出的值为0，为什么不是字符s出现的次数呢？哪里编写错了吗？

Answer 1

    auto s = find_char(a, b, m);
    cout << s << '\n'<< m << endl;

否则m是之前的值。