打印到std :: ostream的时间

Question

I have just started reading a C++ textbook and I am having trouble solving one of the coding problems at the end of the chapter. Here is the question:

Write a program that asks the user to enter an hour value and a minute value. The main() function should then pass these two values to a type void function that displays the two values in the format shown in the following sample run:

Enter the number of hours: 9
Enter the number of minutes: 28
Time: 9:28

my code so far is:

#include <iostream>
using namespace std;
void time(int h, int m);

int main()
{
    int hour, min;

    cout << "enter the number of hours: ";
    cin >> hour;
    cout << "enter the number of minutes: ";
    cin >> min;

    string temp = time(hour, min);

    cout << temp;

    return 0;
}

void time(int h, int m)
{
    string clock;
    clock =
}

What do I do now inside the time(n, m) function?

Thanks.

Answer 1

You can include <iomanip> and set field width and fill so that times like 9:01 are printed properly. And since the function time should just print the time, building and returning a std::string can be omitted. Just print these values:

void time(int hour, int min)
{
    using namespace std;
    cout << "Time: " << hour << ':' << setfill('0') << setw (2) << min << endl;
}

Also note that writing using namespace std; at the beginning of your files is considered bad practice since it causes some of user-defined names (of types, functions, etc.) to become ambiguous. If you want to avoid exhausting prefixing with std:: , use using namespace std; within small scopes so that other functions and other files are not affected.

Answer 2

The question requests "a type void function that displays the two values in the format shown" so the simplest and most correct (because it matches what was asked) solution is:

void time(int h, int m)
{
  cout << "Time: " << h << ":" << m << endl;
}

Your main() function then needs to do nothing but...

  // ... prompt for values as before, then:

  time(hour, min);

  return 0;
}

and then return.

Answer 3

First time() should return a std::string. To format the string inside time() you could use std::ostringstream (header sstream).

Eg:

std::string time(int hour, int minutes)
{
   std::ostringstream oss;
   oss << hour << ":" << minutes;
   return oss.str();
}

Edit: Of course, you could also print hour and minutes directly inside the time(..) function. Or you could pass the time(..) function also a stream argument to let time(..) print it out on that stream.

Answer 4

Your code in main is assuming that time is a string method, the question states void . Your code should be:

#include <iostream> 
using namespace std; 
void time(int h, int m); 

int main() 
{ 
    int hour, min; 

    cout << "enter the number of hours: "; 
    cin >> hour; 
    cout << "enter the number of minutes: "; 
    cin >> min; 

    // Now pass to your time method.
    time(hour, min); 

    return 0; 
} 

void time(int h, int m)     
{     
    cout << "Time: " << h << ':' << m << endl;     
}

and Bob is someone's uncle.