string variable

[cdg]

Could anyone tell me how to correctly assign a variable name to the return
of the function call in this example program. I needed to convert a integer
to a string, using stringstream. However after returning the string I am not
sure how to assign a variable name to it.

#include <iostream>
#include <sstream>
using namespace std;

string Convert(int);

void main ()
{
int num = 123456789;

"???" = Convert(num).c_ str() //***variable here***
}

string Convert(int num)
{
stringstream test;
test << num;

return test.str();
}

[Victor Bazarov]

Re: string variable

cdg wrote:[color=blue]
> Could anyone tell me how to correctly assign a variable name to the return
> of the function call in this example program. I needed to convert a integer
> to a string, using stringstream. However after returning the string I am not
> sure how to assign a variable name to it.
>
> #include <iostream>
> #include <sstream>
> using namespace std;
>
> string Convert(int);
>
> void main ()
> {
> int num = 123456789;[/color]

Here you declare a variable, named 'num', of type 'int', and initialise
it with a number. Seems simple enough, no?
[color=blue]
>
> "???" = Convert(num).c_ str() //***variable here***[/color]

Here, declare another variable, name it something, give it a type
(an appropriate type), and initialise it with a call to 'Convert'.

Now, give it your best shot.
[color=blue]
> }
>
> string Convert(int num)
> {
> stringstream test;
> test << num;
>
> return test.str();
> }
>
>[/color]

V
--
Please remove capital As from my address when replying by mail

[red floyd]

Re: string variable

cdg wrote:[color=blue]
> Could anyone tell me how to correctly assign a variable name to the return
> of the function call in this example program. I needed to convert a integer
> to a string, using stringstream. However after returning the string I am not
> sure how to assign a variable name to it.
>
> #include <iostream>
> #include <sstream>
> using namespace std;
>
> string Convert(int);
>
> void main ()
> {
> int num = 123456789;
>
> "???" = Convert(num).c_ str() //***variable here***
> }
>
> string Convert(int num)
> {
> stringstream test;
> test << num;
>
> return test.str();
> }
>[/color]

Big hint.... What does std::string::c_ str() return? That should give
you an idea as to the variable type.

[cdg]

Re: string variable

Thanks.

I have just started using strings with stringstream, and didn`t realize it
would be quite that simple.

[cdg]

Re: string variable

Could anyone help me with this next problem I am having with this same
example program. I need to get the the string length, and there is an error
message at the "strlen" line.

#include <iostream>
#include <sstream>
using namespace std;

string Convert(int);

void main ()
{
int num = 123456789;
int tmlen(0);
string result;

result = Convert(num).c_ str();

reslen = strlen(result);//***problem here***

cout<<reslen<<e ndl;
}

string Convert(int num)
{
stringstream test;
test << num;

return test.str();
}

[Jim Langston]

Re: string variable

"cdg" <anyone@anywher e.com> wrote in message
news:EspPf.1042 6$Tf3.5711@duke read09...[color=blue]
> Could anyone help me with this next problem I am having with this same
> example program. I need to get the the string length, and there is an
> error
> message at the "strlen" line.
>
> #include <iostream>
> #include <sstream>
> using namespace std;
>
> string Convert(int);
>
> void main ()
> {
> int num = 123456789;
> int tmlen(0);
> string result;
>
> result = Convert(num).c_ str();[/color]

just do result = Convert(num)
or even better yet
std::string result = Convert(num);
[color=blue]
> reslen = strlen(result);//***problem here***[/color]

result.length() ;
[color=blue]
> cout<<reslen<<e ndl;
> }
>
> string Convert(int num)
> {
> stringstream test;
> test << num;
>
> return test.str();
> }
>
>[/color]

[BobR]

Re: string variable


cdg wrote in message ...[color=blue]
> Could anyone help me with this next problem I am having with this same
>example program. I need to get the the string length, and there is an error
>message at the "strlen" line.
>
>#include <iostream>
>#include <sstream>
>using namespace std;
>
>string Convert(int);
>
>void main (){[/color]

int main(){ // ALWAYS returns 'int'
[color=blue]
> int num = 123456789;
> int tmlen(0);[/color]
// > string result;
// > result = Convert(num).c_ str();

std::string result = Convert( num ).c_str();

// > reslen = strlen(result);//***problem here***

size_t reslen( result.size() );
[color=blue]
> cout<<reslen<<e ndl;[/color]

return 0;[color=blue]
>}
>
>string Convert(int num){
> stringstream test;
> test << num;
> return test.str();
>}[/color]

You don't have a book, do you?

Get "Thinking in C++", 2nd ed. Volume 1 by Bruce Eckel
(available for free here. You can buy it in hardcopy too.):

http://www.mindview.net/Books/TICPP/ThinkingInCPP2e.html

Then off to:

https://www.accu.org

--
Bob R
POVrookie

[Peter_Julian]

Re: string variable


"cdg" <anyone@anywher e.com> wrote in message
news:EspPf.1042 6$Tf3.5711@duke read09...
| Could anyone help me with this next problem I am having with this same
| example program. I need to get the the string length, and there is an
error
| message at the "strlen" line.
|
| #include <iostream>
| #include <sstream>
| using namespace std;
|
| string Convert(int);
|
| void main ()
| {
| int num = 123456789;
| int tmlen(0);
| string result;
|
| result = Convert(num).c_ str();
|
| reslen = strlen(result);//***problem here***
|
| cout<<reslen<<e ndl;
| }
|
| string Convert(int num)
| {
| stringstream test;
| test << num;
|
| return test.str();
| }
|

A std::string knows it own size().

#include <iostream>
#include <ostream>
#include <sstream>
#include <string>

template< class T >
std::string Convert(const T& t)
{
std::ostringstr eam oss;
oss << t;
return oss.str();
}

int main()
{
int n = 12345;
std::string s = Convert<int>(n) ;
std::cout << "\nsize of s = " << s.size();
std::cout << "\ns = " << s;

s += Convert<int>(67 89);
std::cout << "\nsize of s = " << s.size();
std::cout << "\ns = " << s;

return 0;
}

/*
size of s = 5
s = 12345
size of s = 9
s = 123456789
*/

[benben]

Re: string variable

> Big hint.... What does std::string::c_ str() return? That should give[color=blue]
> you an idea as to the variable type.[/color]

I hope you haven't misled the OP much.

std::string::c_ str() returns a const char*. But if you do the following:

const char* s = Convert(num).c_ str();

then s will point to invalid memory. To avoid this, copy the content
before it gets destroyed:

string s1 = Convert(num);
string s2 = Convert(num).c_ str();

The call to c_str() is redundant.

Regards,
Ben