Thread: formating numbers

I have a long double that represents a dollar amount, say $1,234.56. If I do just

Code:

long double number = 1234.56;
std::cout<<number;

I get

Code:

1234.56

Is there an IOS flag or something similar I can set to display this number with commas, like this

Code:

1,234.56

Well, there's the somewhat advanced topic of facets and locales that could get you what you want but you're probably better off just using a stringstream to convert the value into a string and then do some string processing on the result to find the '.' character and add the ',' where appropriate.

You are?

Code:

#include <iostream>
#include <locale>

int main()
{
        std::cout.imbue(std::locale(""));
        std::cout << 12942.51 << std::endl;
}

This looks a tiny bit easier to me than doing what you suggest.

Originally Posted by CornedBee

You are?

Code:

#include <iostream>
#include <locale>
 
int main()
{
        std::cout.imbue(std::locale(""));
        std::cout << 12942.51 << std::endl;
}

This looks a tiny bit easier to me than doing what you suggest.

I was actually looking into that. Works good although I don't yet fully understand all the details.

I created a function using stringstreams to manually insert the commas. Not too bad, but it came out to about 40 lines. I think I like 2 lines better

I am going to do some more reading on facets and locales... looks interesting

It's not that complicated. By default, cout is imbued to the C locale, which doesn't do any special formatting. std::locale("") constructs a copy of the system's default locale, which is whatever you specified in the language settings. This locale will format the number according to local conventions. For example, if I ran this on my Windows installation, it would print "12.942,51", because that's the way numbers are formatted in Germany and Austria. (My Linux system is set up with an English locale.)

It was the implementation that I did not quite grasp. I was making it out to be harder than what it is.

Good bit of information to know.... Thanks!