C / C++ / MFC

3-Jun-02 16:35

Hi All,

what seems to be the problem of this code:

#include <string>
#include <iostream.h>
int main()
{
std::string str1="Hello World";
std::str2=str1.substr(6,5);
return 0;
}

I get an error "error C2039: 'str2' : is not a member of 'std'"

Thansk/Regards
Sidney

Thanks/Regards
Sidney

Rama Krishna Vavilala3-Jun-02 16:39

3-Jun-02 16:39

Sidney wrote:
std::str2=str1.substr(6,5);

should be

std::string str2 = str1.substr(6,5);

Smile | :)

Sidney3-Jun-02 16:44

3-Jun-02 16:44

Hey Rama!

Thanks Smile | :)

Sidney3-Jun-02 16:48

3-Jun-02 16:48

One more quick question...

why is it I can's directly output the str2 using cout ??

std::string str1="Hello World";
std::string str2=str1.substr(6,5);
cout << str2;

I get this error: "error C2679: binary '<<' : no operator defined which takes a right-hand operand of type 'class std::basic_string<char,struct std::char_traits<char="">,class std::allocator<char> >' (or there is no acc

Thanks/Regards
Sidney

Rama Krishna Vavilala3-Jun-02 16:53

3-Jun-02 16:53

You should use iostream not isotream.h

#include <iostream>

not

#include <iostream.h>

Then you need to prefix cout with std::

std::cout << str2;

Rama Krishna
When I am near, do not fear

Sidney3-Jun-02 16:58

3-Jun-02 16:58

Oh I see... can I store the value of str2 in a new variable? can you show me on how to do this... I'm sorry I'm new in C++ I'm still studying.

I really appreciate your help =)

Thanks/Regards
Sidney

Rama Krishna Vavilala3-Jun-02 17:01

3-Jun-02 17:01

Yiur original code is right just prefixe cout with std::cout. I will work. Try and see Smile | :)

Sidney3-Jun-02 17:08

3-Jun-02 17:08

Yes it did... It's working now Smile | :)

One last question... after this I'll let you go Big Grin | :-D

How can I pass the value of str2 in a new variable? example:

int main(){

char var[100];
std::string str1="Hello World";
std::string str2=str1.substr(1,5);
std::cout << str2;
//how shoud I transfer it to var variable??
var = ???(str2);
}

Thanks/Regards
Sidney

Rama Krishna Vavilala3-Jun-02 17:19

3-Jun-02 17:19

Correct way to do this is,

str2.copy(var, 100);

Sidney3-Jun-02 17:15

3-Jun-02 17:15

Thanks Rama!! your the base Wink | ;)

Thanks/Regards
Sidney

GetMessage

wilche3-Jun-02 15:33

wilche

3-Jun-02 15:33

Hi Everyone,

I need some help!!!

I have been retrieving my messages from the message queue in my thread using the GetMessage().

I've placed the message inside the MSG structure and retrieve the messaage contents by referencing msg.wParam. msg.wParam is an UINT value that represents the address of msg content, in this case, a dynamically allocated char * pointer.

After using this string, I wanted to deallocate the memory for this char *ptr, doing this.

delete (char *) msg.wParam;

It compiles but didn't work. As suspected, msg.wParam isn't a ptr, it's an address! So I tried this.

char *tmp;
tmp = (char *) msg.wParam;
delete tmp;

It compiles Same problem. So what can I do?
Everytime a new msg comes, the information in msg.wParam is rewritten. But I'm pretty sure that the memory allocation remains!
Confused | :confused:

Any help on this problem is greatly appreciated! Thanks!
wilche

John M. Drescher3-Jun-02 17:13

John M. Drescher

3-Jun-02 17:13

try
delete [] reinterpret_cast<char*>(msg.wParam);

Rama Krishna Vavilala3-Jun-02 17:16

3-Jun-02 17:16

John M. Drescher wrote:
delete [] reinterpret_cast(msg.wParam);

Oops I missed that in my reply. Thanks Smile | :)

wilche3-Jun-02 17:25

wilche

3-Jun-02 17:25

Thanks! that works!
uh could you explain why it works?
greatly appreciated!

wilche