sstream

[Michael]

Hi,

I am using Quincy99 and do not have sstream library to use. I want to
convert string "123" to integer 123. How to get the work done? Thanks!

#include <iostream>
#include <string>

using namespace std;

int main ()
{
string a ("123");

int b;
b=int(a);

cout << b;

return 0;
}


Thanks a lot!
Michael

 

[David Harmon]

On Tue, 19 Jun 2007 11:05:44 -0700 in comp.lang.c++, Michael

I am using Quincy99 and do not have sstream library to use. I want to
convert string "123" to integer 123. How to get the work done? Thanks!

Look for old C strtol()

 

[Bharath]

On Tue, 19 Jun 2007 11:05:44 -0700 in comp.lang.c++, Michael


Look for old C strtol()

why not this -
#include <stdlib.h>
i = atoi(s);

Bharath

 

[Marcus Kwok]

why not this -
#include <stdlib.h>
i = atoi(s);

There is no way to tell whether or not atoi() fails.

 

[Victor Bazarov]

why not this -
#include <stdlib.h>
i = atoi(s);

'atoi' is not a very good function. E.g. it doesn't distinguish between
a string that contains "0" and a string that does not contain a number.

V

 

[Default User]

'atoi' is not a very good function. E.g. it doesn't distinguish
between a string that contains "0" and a string that does not contain
a number.

There's a further problem (or maybe a generalization of that one) in
that a string with an initial sequence of numerals will be partly
converted to an integer, again with no way of telling what happened.



Brian

 

[Michael]

There is no way to tell whether or not atoi() fails.

Thanks a lot, Experts. How to let the following code run?

#include <iostream>
#include <string>
#include <stdlib.h>

using namespace std;

int main ()
{
string a;
getline(cin,a);

char * pEnd;

int b;
b=strtol (a,&pEnd,10);

cout << b;

return 0;
}

 

[Victor Bazarov]

Thanks a lot, Experts. How to let the following code run?

#include <iostream>
#include <string>
#include <stdlib.h>

using namespace std;

int main ()
{
string a;
getline(cin,a);

char * pEnd;

int b;
b=strtol (a,&pEnd,10);

Probably

b=strtol (a.c_str(),&pEnd,10);

cout << b;

return 0;
}

V

 

[Default User]

Please trim quoted material to the minimum needed for context.
Especially trim quoted signatures like the one above.

Thanks a lot, Experts. How to let the following code run?

#include <iostream>
#include <string>
#include <stdlib.h>

using namespace std;

int main ()
{
string a;
getline(cin,a);

char * pEnd;

int b;
b=strtol (a,&pEnd,10);

1. You can't pass a string to strtol(). It requires a const char*. Pass
a.c_str().

2. There's very little point in passing a pointer to pEnd to strtol()
and then not use it.

You'll need a couple of checks. One is:

if (pEnd == a.c_str())
{
// no conversion, handle it
}
else if (*pEnd != 0) // not at end of string
{
// partial conversion, handle it
}

You also should check for overflow, using errno. If errno == ERANGE,
then look at the return value. It will be either LONG_MAX or LONG_MIN,
telling you which way it would have overflowed.

cout << b;

return 0;
}

Brian