Add an integer to a string without using std::stringstream

[Christopher Benson-Manica]

If std::stringstreams are unavailable, how would you go about adding
an integer (or unsigned integer) to a string?

 

[John Harrison]

If std::stringstreams are unavailable, how would you go about adding
an integer (or unsigned integer) to a string?

sprintf the integer to a C string and then append that C string to the C++
string. That would probably be the way I would do it in any case.

John

 

[Mike Wahler]

If std::stringstreams are unavailable, how would you go about adding
an integer (or unsigned integer) to a string?

#include <cstdio>
#include <iostream>
#include <limits>
#include <string>

int main()
{
std::string s("Hello");
int i(42);
char *tmp = new char[std::numeric_limits<int>::digits10 + 2];
std::sprintf(tmp, "%d", i);
s += tmp;
std::cout << s << '\n'; /* prints "Hello42"
delete[] tmp;
return 0;
}

-Mike

 

[Siemel Naran]

If std::stringstreams are unavailable, how would you go about adding
an integer (or unsigned integer) to a string?

In addition to sprintf as others point out, there is also istrstream -- need
to #include <strstream.h>. Not sure if it is deprecated or even still part
of the standard, but imagine it is fine.

 

[Buster]

If std::stringstreams are unavailable, how would you go about adding
an integer (or unsigned integer) to a string?

#include <limits>
#include <string>
#define X *--o='0'+(x%10);x/=10;
#define O while(x){*--o=',';X if(x)X if(x)X}

template <typename Integer>
void append_int (Integer x, std::string & s)
{
char buffer [std::numeric_limits <Integer>::digits10 * 4 / 3 + 2];
char * o = buffer + sizeof buffer;

if(x<0){if((x=-(x+1))%10-9){*--o='1'+(x%10);x/=10;}
else{*--o='0';x/=10;++x;}X if(x)X O*--o='-';}
else if(x){X if(x)X if(x)X O}else{*--o='0';}

s.append (o, buffer + sizeof buffer);
}

 

[Michiel Salters]

In addition to sprintf as others point out, there is also istrstream -- need
to #include <strstream.h>. Not sure if it is deprecated or even still part
of the standard, but imagine it is fine.

std::[io]strstream, in <strstream>, is standard but deprecated.