使用定界符C ++将字符串解析为整数

Question

I am trying to make a callrate calculater where the input will be done as following: hh:mm

After this i want to parse that string into two ints with only ':' as a delimiter. This solution i got here seems to only work with space, but I want the delimiter to be colons, and not space. Is there even a possible way to do this?

#include <iomanip>
#include <iostream>
#include <string>
#include <sstream>

using namespace std;

int main() {

    string input;
    getline(cin, input);
    istringstream is(input);
    int hours, minutes; 

    is >> hours>> minutes;

    cout << timmar << endl;
    cout << minuter << endl;
}

Answer 1

Read the delimiter character into another variable.

char colon;

is >> hours >> colon >> minutes;
if (colon != ':') {
    cout << "Incorrect delimiter: " << colon << '\n';
}

Answer 2

Instead of expecting a default delimiter I'd use a custom manipulator to specifically deal with the delimiter:

std::istream& colon(std::istream& in) {
    if (in.peek() != ':' || std::isspace(in.ignore().peek())) {
        in.setstate(std::ios_base::failbit);
    }
    return in;
}
// ...
int hours, minutes;
if (in >> hours >> colon >> minutes) {
    // process the input
}

Using this manipulator avoid spaces in the proximity of the colon being considered valid: the normal input operation start off with skipping space. Reading the delimiter simply into a variable would allow spaces in front of the delimiter and also allow any non-space character as a delimiter. Carrying on reading directly after delimiter would, again, allow spaces after the delimiter. Using the colon manipulator above turns both of these cases into an error. ... and, of course, you always need to check after reading and before using the results whether input was successful.

---

An entirely different approach to the same problem is to redefine the stream's notation of whitespace . The idea here is to take advantage of the stream's std::locale and to imbue() a std::locale which considers the desired separator, eg, : as the only "whitespace". Below is a complete example demonstrating that idea. It uses a separate std::istream with a custom std::locale to avoid changing how std::cin works. However, it still uses std::cin stream buffer, ie, it reads from the same source as std::cin .

#include <algorithm>
#include <locale>

struct myctype_base {
    std::ctype<char>::mask table[std::ctype<char>::table_size];
    myctype_base(unsigned char c) {
        table[c] |= std::ctype_base::space;
    }
};
struct myctype
    : private myctype_base
    , std::ctype<char> {
public:
    myctype(char delimiter)
        : myctype_base(delimiter)
        , std::ctype<char>(myctype_base::table) {
    }
};

int main() {
    std::locale loc(std::locale(), new myctype(':'));
    std::istream in(std::cin.rdbuf());
    in.imbue(loc);

    int hours, minutes;
    if (in >> hours >> minutes) {
        std::cout << "read hours=" << hours << " minutes=" << minutes << "\n";
    }
    else {
        std::cout << "failed to read input\n";
    }
}