Re: Help add commas to int on console output
On Apr 1, 5:14 am, Martin York <Martin.YorkAma...@gmail.com> wrote:
On Mar 31, 6:15 pm, yogi_bear_79 <yogi_bear...@yahoo.com> wrote:
I am passing a whole number integer to this function, it converts the
integer to a string, then I want to add commas so a number like
1234567 shows as 1,234,567. I am a little stuck, I belive the loop is
reading the string from right to left which led me to try decrementing
the loop, but a number like 12345 shows up like 123,45. Or is there a
better way all together to achive ths.
string toStr(int &i)
{
std::string s;
std::stringstream out;
out << i;
s = out.str();
for(size_t x = s.size(); x > 0; x--){
if(x != s.size() && x%3 == 0)
s.insert(x,",");
}
return s;
}
You can use the locale objects to do this for you.
Of course, there's a good chance that there is already a locale
present which does it. Or not---it depends somewhat on the
compiler and the system. On my Sparc, about the only locale
installed, other than C, is en_US.UTF-8, which doesn't do the
job. And g++ won't find it anyway, although Sun CC does. On my
Linux machine, en_US and de_DE both insert commas, but fr_FR
doesn't. (Logically, it should insert spaces.) And I have no
idea how locales are named under Windows, in order to test it
there.
For the rest, excellent code, but I'd add a few comments,
because std::locale does have some strange and unexpected ways
of doing things.
#include <sstream>
#include <iostream>
#include <locale>
#include <string>
// custom numeric punctuation facet
struct Punct: std::numpunct<char>
{
char do_thousands_sep () const
{
return ',';
}
std::string do_grouping () const
{
return "\3";
}
};
The two functions above are virtual in the base class. I'd have
repeated the virtual here (and declared them protected, since
that's what they are in the base class).
I'd also explain why do_grouping returns a string with binary
values, except that I can't figure that one out myself; it just
does. (The equivalent function in C returns a char const*, but
in this case, "char" is not a character, but a small integer,
and the C++ equivalent would be std::vector<char>. Given the
actual use, of course, having the C++ function return a char
const* would make perfect sense as well.)
std::string toStr(int x,std::locale const& l)
{
std::stringstream stream;
stream.imbue(l);
stream << x;
return stream.str();
}
int main()
{
// construct a custom punctuation facet
std::numpunct<char>* punct = new Punct;
I'd also have added a comment here, to the effect that the
constructed locale will delete the object. Otherwise, it should
make anyone not aware of this fact wonder. (As it is, it looks
to someone unfamiliar with locales that you've been too
influenced by Java.)
// construct a locale containing the custom facet
const std::locale locale(std::cout.getloc(),punct);
std::cout.imbue(locale);
std::cout << "Val: " << 1234556 << std::endl;
std::cout << "From String: " << toStr(123456789,locale) <<
std::endl;
}
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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