Taking integers from a string

Hello, this is my first question on this site. I have a string with a date in it, like "17/02/1943", in the format dd/mm/yyyy. I need to get the date from this string, and put it into my Date struct, which has three int's for Day, Month and Year. How would I go about getting the numbers out, would I get substrings and cast them or something?

There are a couple different ways... The first involves using the atoi function:

Code:

---

#include <string>
#include <iostream>
#include <cstdlib>
using namespace std;

int main()
{
    string str("14/05/1988");
    int day, month, year;

    day = atoi( str.substr(0,2).c_str() );
    month = atoi( str.substr(3,2).c_str() );
    year = atoi( str.substr(6,4).c_str() );

    cout << "Day: " << day << " Month: " << month << " Year: " << year << endl;

    return 0;
}

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Or you can use string streams:

Code:

---

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

int main()
{
    string str("14/05/1988");
    int day, month, year;
    istringstream sstr(str);
    char dummy;

    sstr >> day >> dummy >> month >> dummy >> year;

    cout << "Day: " << day << " Month: " << month << " Year: " << year << endl;

    return 0;
}

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Both ways should output the same thing:

Code:

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Day: 14 Month: 5 Year: 1988

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Not too sure about that istringstream thing, and our lecturer looks down on anyone who uses C-style libraries or functions (i.e. cstdlib.h, cstring.h).

I can get the substrings to just have the number I want ("32"), but can't convert them to int format. <static_cast><int> just gives me heaps of errors.

Here's my code, Date is a struct:

Code:

---

#include <iostream>
#include <string>
#include "Date.h"

using std::cout;
using std::string;

Date fileInputDate(string entry)
{
        Date output;
        output.Day = static_cast<int>(entry.substr(0,2));
        output.Month = static_cast<int>(entry.substr(3,2));
        output.Year = static_cast<int>(entry.substr(6,4));
        return output;
}

---

This gives me 3 C2440 errors. Is there anyway to do this without using C-style commands or any other libraries?

>Is there anyway to do this without using C-style commands or any other libraries?
You could always do the conversion manually. For small numbers like those in a date, you don't need to worry about the problematic cases that more sophisticated string-to-integer libraries must consider. The conversion is a simple loop.

Code:

---

Date fileInputDate(string entry)
{
  Date output; // Assumes that output is zero initialized

  for (int i = 0; i < 2; i++) {
    output.Day = 10 * output.Day + (entry[i] - '0');
  }
  for (int i = 3; i < 5; i++) {
    output.Month = 10 * output.Month + (entry[i] - '0');
  }
  for (int i = 6; i < 10; i++) {
    output.Year = 10 * output.Year + (entry[i] - '0');
  }

  return output;
}

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