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Question on converting unsigned long to std::string

Hi,

I need to convert unsigned long data to a std::string, I googled a bit
to see if the string class supports any methods to achieve this - but
didnt find any, I think of using sprintf and converting to a char buf
and then putting it back in std::string -

is anyone aware of any other way?

Thanks
/R
Oct 10 '08 #1
4 6181
On Thu, 09 Oct 2008 21:12:51 -0700, Ramesh wrote:
Hi,

I need to convert unsigned long data to a std::string, I googled a bit
to see if the string class supports any methods to achieve this - but
didnt find any, I think of using sprintf and converting to a char buf
and then putting it back in std::string -

is anyone aware of any other way?

Thanks
/R
istringstream is one way without resorting to the C libraries

see this example

http://www.nylxs.com/docs/workshops/pharm.C.html

look around line 670
668 float Weight::wgt(const string &descr)
669 {
670 string errormsg("ERROR: enter a number followed by either \"kilograms\" or \"pounds\"");
671 istringstream stream1;
672 stream1.str(descr);
673 if (!(stream1>>wgt_))
674 throw errormsg;
675 if(!(stream1>>unit_))
676 throw errormsg;
677 errormsg = "ERROR: enter either \"kilograms\" or \"pounds\"";
678 if( unit_ == "kg" || unit_ == "k" || unit_ == "kilo" || unit_ == "kilogram"|| unit_ == "kilograms"){
679 unit_ = "kg";
680 }else if( unit_ == "lb" || unit_ == "pound" || unit_ == "pd"|| unit_ == "pounds" ){
681 wgt_ = wgt_ * 0.45454545;
682 }else{
683 throw errormsg;
684 }
685 return wgt_;
686 }
687

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© Copyright for the Digital Millennium

Oct 10 '08 #2
On Oct 10, 6:23 am, Ruben <ru...@www2.mrbrklyn.comwrote:
istringstream is one way without resorting to the C libraries
Since he wants to convert a number to a string, I'd rather use
ostringstream. An example can be found at:

http://www.parashift.com/c++-faq-lit....html#faq-39.1

-- Daniel
Oct 10 '08 #3
Ramesh wrote:
Hi,

I need to convert unsigned long data to a std::string, I googled a bit
to see if the string class supports any methods to achieve this - but
didnt find any, I think of using sprintf and converting to a char buf
and then putting it back in std::string -

is anyone aware of any other way?
If you are used to sprintf but want something that deals with std::string
instead, you could try this:

bool strprintf ( std::string & buffer, char const * format, ... ) {
while ( true ) {
buffer.resize( buffer.capacity() );
int old_length = buffer.size();
std::va_list aq;
va_start( aq, format );
int length_needed =
vsnprintf( &buffer[0], old_length + 1, format, aq );
va_end( aq );
if ( length_needed < 0 ) {
return ( false );
}
buffer.resize( length_needed );
if ( length_needed <= old_length ) {
return ( true );
}
}
}
WARNING: the above is not standard compliant; it assumes that std::string is
contiguous (as far as I know, all implementations are, and it will be
required by the next iteration of the standard C++0X); also it requires
that is is legal to write a trailing 0 behind the string. Also, it assumes
that vsnprintf() conforms to C99 or C++0X. Thus, you have to test this
carefully.
Best

Kai-Uwe Bux
Oct 10 '08 #4
Ramesh wrote:
is anyone aware of any other way?
I really can't understand why two people have already answered your
question with overly long and complicated answers, which are also
basically just wrong. Come on, people, keep answers simple and
concentrate on the *basics*.

What you want is this:

std::ostringstream os;
os << yourUnsignedValue;
std::string theValueAsString = os.str();
Oct 10 '08 #5

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