Return integer value as string for date formatting

Question

I have function that has three integer values, representing year, month and day. I want to return these values with dashes '-' in between, as in common date format.

e.g.:

int main() {
    cout << myfunction() << endl; // this should display like this 2014-04-15
}

string myfunction() {
    int year = 2014;
    int month = 04;
    int day = 15;
    // I want to return this value like this
    return year-month-day;//2014-04-15
}

Can someone help me?

Take a look at [`std::to_string`](http://en.cppreference.com/w/cpp/string/basic_string/to_string) — Captain Obvlious, Apr 15 '14 at 17:56
All the replies given so far misses the problem of 0-padding (e.g. April -> 4 -> output `04`). [It's very easy and clear to do that with `sprintf()`](http://stackoverflow.com/a/23091285/1629821); it's a bit more work with `` string streams. — Mr.C64, Apr 15 '14 at 18:26

score 2 · Answer 1 · 2014-04-15T19:05:59.323

2

#include <sstream>
#include <iomanip>

...

std::stringstream ss;
ss << std::setfill('0') << std::setw(4) << year << "-"
   << std::setw(2) << month << "-" << std::setw(2) << day;
return ss.str();

edited Apr 15 '14 at 19:05

answered Apr 15 '14 at 18:00

1

Are you sure the OP wants to print April as `4`, or would `04` be better? – Mr.C64 Apr 15 '14 at 18:28
@Mr.C64 thanks. I edited the answer based on your suggestion. – Apr 15 '14 at 19:06

4pie0 · Accepted Answer · 2014-04-15T18:50:48.630

1

In C++03 you can use std::ostringstream class to format a string using operator<< :

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

std::string myfunction() {
    int year=2014;
    int month=04;
    int day=15;

    std::ostringstream oss;
    oss << year << "-" << std::setw(2) << std::setfill('0') 
                                                     << month << "-" << day;
    return oss.str();
           ^^^^^^^^^ // this will yield a formatted string that oss contains
}

In C++11 you can use std::to_string and operator+ to concatenate strings:

#include <string>

std::string myfunction() {
    int year=2014;
    int month=04;
    int day=15;

    std::string s = to_string( year) 
                    + "-" + to_string(month)
                    + "-" + to_string(day);
    return s;
}

however to_string doesn't offer formatting option. If you want to specify format, again, you should look into string stream.

edited Apr 15 '14 at 18:50

answered Apr 15 '14 at 18:00

4pie0

29,204
9
82
118

Are you sure the OP wants to print April as `4`, or would `04` be better? – Mr.C64 Apr 15 '14 at 18:28
changed to print zeroes, thank you – 4pie0 Apr 15 '14 at 18:39
You're welcome. Maybe the second code with `to_string()` needs a fix as well? – Mr.C64 Apr 15 '14 at 18:40
added the note about formatting to_string, thank you – 4pie0 Apr 15 '14 at 18:51

score 1 · Answer 3 · answered Apr 15 '14 at 18:01

1

also, if you don't have C++11, look at boost::lexical_cast(...), or if you don't want boost, look at stringstream.

stringstream ss;
ss << first << "-" << second << "-" << third << endl;
return ss.str();

that have to work.

answered Apr 15 '14 at 18:01

Arkady

2,084
3
27
48

score 1 · Answer 4 · answered Apr 15 '14 at 18:01

1

ostringstream oss;
oss << year << '-' << month << '-' << day;

return oss.str();

answered Apr 15 '14 at 18:01

Yifu Wang

313
2
9

score 1 · Answer 5 · answered Apr 15 '14 at 18:02

1

You can use a string stream.

string myfunction(){
    int year=2014;
    int month=04;
    int day=15;
    stringstream ss;
    ss << year << "-" << month << "-" << day;
    return ss.str();
}

Don't forget to include sstream header.

answered Apr 15 '14 at 18:02

Elie Génard

1,673
3
21
34

score 0 · Answer 6 · answered Apr 15 '14 at 18:08

0

If you do not want to use STL, you can also resort to C-style function _itoa. Here is a link to the documentation:

http://msdn.microsoft.com/en-us/library/yakksftt.aspx

But I do suggest you to use stringstream like others are suggesting.

answered Apr 15 '14 at 18:08

santahopar

2,933
2
29
50

score 0 · Answer 7 · edited May 23 '17 at 11:57

Even in C++ code, I like printf-like format specifiers (in this case, to be used with sprintf()).

You may want to consider this compilable code:

#include <stdio.h>
#include <iostream>
#include <string>

std::string ToString(int year, int month, int day) {
    char buffer[11];
    // YYYY-MM-DD
    // 1234567890
    //          10 + NUL --> 11 characters in buffer

    sprintf(buffer, "%04d-%02d-%02d", year, month, day);
    // sprintf_s on MSVC would be better (and it implicitly gets the dest buffer size).

    return buffer;
}

int main() {
    std::cout << ToString(2014, 4, 15) << std::endl;
}

Output is 2014-04-15, as requested.

PS
If you want to use C++ string streams (from <sstream>), then you should pay attention to padding with a leading 0 the months and days having one digit. For that purpose, consider this StackOverflow question and related answers. The key point is to use setfill('0') and setw(2) for padding.

Return integer value as string for date formatting

7 Answers7