Data type "string with "#include <string>" ?

[Anonymous]

Dear all,
I'd like to return a string from a defined function but I just get failed to do it. For example:

#include <iostream>
#include <string>

string mytest(void);

int main(void)
{
  cout >> myTest();
  system("pause");
  return 0;
}

string mytest(void)
{
return "Happy";
}

Does DEV-Cpp provide "string" data type?
Or I just missed something so that it failed?
Thanks a lot.

[Liviu Nicolescu]

There are 2 ways to use standard C++ types ( such as string, vector, list, etc.).

Either you add "using namespace std;" ( without the quotes) after including the headers, or use the qualified names of the objects you want to use.

Ex. 1:
#include <iostream>
#include <string>
using namespace std;

string mytest(void);

int main(void)
{
cout >> myTest();
system("pause");
return 0;
}

string mytest(void)
{
return "Happy";
}

Ex. 2
#include <iostream>
#include <string>

std::string mytest(void);

int main(void)
{
std::cout >> myTest();
system("pause");
return 0;
}

std::string mytest(void)
{
return "Happy";
}

[Wayne Keen]

First important point, Dev-CPP is *not* a compiler that provides or denies functionality - it is an IDE that runs the GCC compiler.  This is important to realize, because it enables you to frame and search on questions..

Next.  Your code did not work because of some typos and an error.  First, C++ is case sensitive, so

mytest

is not the same as

myTest

but you used them interchangably.  Next

cout >> myTest();

makes no sense.  What you want to do is take the output of myTest() and put it out into the stream, which is done as follows

cout << myTest();

You also left out

using namespace std;

or equivalent.

This is why you have to be careful when coding a new concept...there was nothing wrong with your design, the implementation was just careless (something I have done on more than one occasion...in the last hour).  The following code compiles and runs per your design...Dev 4.9.8.1/Windows XP

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

string myTest(void);

int main(void)
{
cout << myTest();
system("pause");
return 0;
}

string myTest(void)
{
return "Happy\n";

Wayne

[Wayne Keen]

Liviu,

Didn't notice the other errors in the code eh?

:-)

Is OK, most of the time you kick my butt on debugging.

Wayne

[Wayne Keen]

Way,

It is always a good idea to post your full compile log with your code, it can help if you have some other problem...post the full log, not just any errors you might see..

Wayne

[Anonymous]

Thank you very much!I did solve the problem.
My main problem is to put "using namespace std;"
after the declairation of the function. I'm sorry
that I mistyped the source code when I post this 
thread. And thanks a lot to Wayne that you gave
me many advices. Thank you both!

WayRe

[Wayne Keen]

WayRe,

**NEVER** type code into a post.  Copy and paste the exact code that you are trying to compile.  It is far easier and avoids misunderstandings.

Wayne

[Liviu Nicolescu]

Wayne,

I was very tired last night when I wrote the post above and I didn't notice the errors.

I'm sorry if you find that I "kick your butt on debugging". That is not what I meant. I just want to give a hand when I can and have time. That's all. Excuse me if I offended you.

Liviu

[Wayne Keen]

No, Liviu, I was *complimenting* you for your debugging skills!  (Telling you yours are better than mine)

In pointing out the other errors, I was trying to be humorous, but obviously I did it quite badly...

My turn to apologize,

Wayne

[Liviu Nicolescu]

Wayne,

I'm sorry I didn't understand correctly what you wanted to say. I am not a native english speaker and my knowledge of every day english is not very good.

Thank you for your compliments. I really appreciate it coming from you.

Liviu

[Wayne Keen]

You do fine with English, and are great with helping with C++!

Sometimes the help folks give get taken for granted, I am trying to improve on recognizing the good work that you and others do out of the goodness of your heart, and the skill of your brain.

Have a great day!

Wayne

[Liviu Nicolescu]

Thank you again, Wayne.

BTW, it's almost night here in Romania :-)

Liviu

[Wayne Keen]

Good evening then!

:-)

I am about to take a late lunchtime bike ride...

I am toooo fat

Wayne

[Wayne Keen]

Made it through a low (~ 16 mph), 12.75 miles...

I live in Florida in the USA, so its a little warm this time of year...

:-)

Wayne

[Anonymous]

Hello Wayne and everybody,

      I have another question maybe someone could help me. I want to output a formatted string from keyboard input, as below:

     #include <iostream>
     #include <cstdlib>
     #include <string>
     using namespace std;
     int main(void)
     {
        string str;
        cout<<"Input a string : "<<endl;
        cin>>str;
        printf("%20s\n",str);
        system("pause");
        return 0;
     }

But I get warning message during compiling :
F:/test2.cpp: In function `int main()':
F:/test2.cpp:11: warning: cannot pass objects of non-POD type `struct std::string' through `...'

Since this had been successfully compiled,I tried to run it but I got strange output......Thanks a lot!

[Liviu Nicolescu]

It is not a very good idea to mix C and C++ functions.

But if you do that, you must use the proper arguments.

You might want to check this link:
http://www.cplusplus.com/ref/cstdio/printf.html.

For your specific problem, the answer is:
printf("%20s\n",str.c_str());

The c_str() function of the class std::string returns a const char* to the contained string.
You must use that because the printf function takes as arguments only simple C types: char, int, float, etc. or pointers.

[Anonymous]

Wow, it works! Thank you so much nliviu. Everybody here are so kind and so cool.
Both of you are my leading card. *^_^*