Super newbie questions

1-

Code:

---

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

string S = "lalala";
string B = S.substr(1,2);
cout << B;

---

This syntax error... I want to make it display "la" for example
Can you show a good substring usage to me

Btw it said string isnt a type and substr isnt declared :/

2- I want a IntegerToString function please (think I can make one but want to know if there is a native or included-in-header one)
and StringToInteger (same content with other paranthesis)


Thanks for replies

(I use Dev-C++ btw)

string is part of the std namespace, so it should be be std::string.
Ot alternatively, you add "using namespace std;" and it will compile.

Code:

---

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

int main()
{
        string s = "number: ";
        s += int(88);
        cout << s << endl;
        return 0;
}
// output:
// number: X

---

At least C++ makes me laugh Out LOUD ! ! !

Perhaps you want "using namespace std" or "std::string"?

stringstream (include <sstream>) will do string to integer and integer to string. Strinstream corresponds (roughly) to cin and cout as the sscanf and sprintf does to scanf and printf. For example:

Code:

---

...

  stringstream ss;
  ss << 10;
  string s;
  ss >> s;
  cout << 10 << " as a string is \"" << s << "\"" << endl;
...

---

--
Mats

Quote:

---

Originally Posted by matsp

Perhaps you want "using namespace std" or "std::string"?

stringstream (include <sstream>) will do string to integer and integer to string. Strinstream corresponds (roughly) to cin and cout as the sscanf and sprintf does to scanf and printf. For example:

Code:

---

...

  stringstream ss;
  ss << 10;
  string s;
  ss >> s;
  cout << 10 << " as a string is \"" << s << "\"" << endl;
...

---

--
Mats

---

it failed to compile. what header to use?

Quote:

---

Originally Posted by manav

it failed to compile. what header to use?

---

I said you need <sstream>, and of course needs <string> as well.

--
Mats

Code:

---

#include <iostream.h>
#include <string>
using namespace std

int main()
{
string S = "lalala";
string B = S.substr(1,2);
cout << B;
return 0;
}

---

Ok like this ? Sorry Im connecting from internet cafe (dont have internet in home) so I dont think I can test now...

lol! :D sorry i missed it!

i was trying strstream, stringstream etc. etc.

It is missing a semicolon (after using...) and there is no such thing as <iostream.h> (that's <iostream>).

Also keep in mind that the first index in strings (among most other things in C++) is 0, in case you want to extract "la", rather than "al".

first index is 0 okay thanks for the tip (so its substr(0,2))
well I have a iostream.h that includes iostream in it
but okay I'll use iostream

Anyway will it work or not
As I said I cant test it

The STL usually works to perfection, provided you can use it. Nevertheless I tested:

Code:

---

#include <iostream>
#include <ostream>
#include <string>
int main ( )
{
    std::cout << '\"' << std::string( "lalala" ).substr( 0, 2 ) << '\"' << std::endl;
}

---

I came out with:
"la"
Press any key to continue . . .


Next time, just wait until you get home.

Code:

---

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

int main()
{
string S = "lalala";
string B = S.substr(0,2);
cout << B << endl;
system("Pause");
return 0;
}

---

working thanks so much

----------------------------------------------

I have another question

File Editor example of Dev-C++ reads the content of file as LPSTR
string s = <Some LPSTR var> is ok or do I need something different for converting between LPSTR and string ?

LPSTR, if I remember correctly, is just an alias for char *. If you're working with legacy code and you need C strings out of a string object, call its' c_str() method.

... so ???

string s = c_str(<LPSTR variable>) ?

how to convert it back to LPSTR then ?

Code:

---

void legacy_foo( char * param );

// ...

legacy_foo ( my_string.c_str() );

---

But there is little sense in working with C strings unless you absolutely must.

Have a look Mats:

Code:

---

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

int main()
{
        sringstream sinout;
        sinout << "number: " << 13 << "is un-unlucky!";
        string s;
        sinout >> s;
        cout << s << endl;
        return 0;
}

---

Quote:

---

error C2065: 'sringstream' : undeclared identifier
c:\my\src\cpp\test-bed\test-bed.cpp(94) : error C2146: syntax error : missing ';' before identifier 'sinout'

---

Argh, come on people. Effort! manav, just read the error: what is the typo supposed to be written as? You can do it.

i can't! :( sorry!! what's the typo?

EDIT: damn! so sorry citizen! so sorry Mats! :( :( :( :( :( :( :( :( :(

Quote:

---

Originally Posted by manav

i can't! :( sorry!! what's the typo?

---

sringstream should be stringstream.

Because it's such a long (and single case) name, it's hard to spot the missing t.

--
Mats

Quote:

---

Because it's such a long (and single case) name, it's hard to spot the missing t.

---

Slightly off topic:
I have been known to #include <iosteam>

Code:

---

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

int main()
{
        stringstream sinout;
        sinout << "number: " << 13 << "is un-unlucky!";
        string s;
        sinout >> s;
        cout << s << endl;
        return 0;
}

---

compiles fine! :)
runs strange!! :(

output>>
number:

Yes, stringstream, like iostreams, stops reading strings on encountering a space - use getline if you want to avoid that. Which is one reason my example didn't include any text [the other reason is that I'm too lazy].

--
Mats

That output is expected, since "number:" is the first substring in the stream before the first whitespace character.

yeah . . .
i again wish that this was possible:

Code:

---

string s;
s << "number:" << 13 << " is un-unlucky!";

---

Quote:

---

Originally Posted by manav

yeah . . .
i again wish that this was possible:

Code:

---

string s;
s << "number:" << 13 << " is un-unlucky!";

---

---

This will do what you want (I'm 99% sure)

Code:

---

stringstream ss;
ss << "number:" << 13 << " is un-unlucky!";
string s = ss.str();

---

--
Mats

We could modify your example to work as you apparently want it to work:

Code:

---

stringstream sinout;
sinout << "number: " << 13 << "is un-unlucky!";
string s(sinout.str());
cout << s << endl;

---

thanks Mats! :)
it fails laserlight! just the same as i posted!

Quote:

---

it fails laserlight! just the same as i posted!

---

I think you looked at my accidental posting... I hit the "post quick reply" button while trying to edit your example.

wow! the speedy helpers! :) but very nice! all of you! thanks!