Like Tree2Likes
  • 1 Post By grumpy
  • 1 Post By laserlight

StringStream

This is a discussion on StringStream within the C++ Programming forums, part of the General Programming Boards category; Ah, after I read carefully about stringstream. I have some code below: Code: int main(){ //string to Int /* ******************************************** ...

  1. #1
    hqt
    hqt is offline
    Registered User
    Join Date
    Aug 2011
    Posts
    115

    Question StringStream

    Ah, after I read carefully about stringstream. I have some code below:
    Code:
    int main(){
    //string to Int
    /* ******************************************** */
        stringstream ss;
        printf("FIRST TEST\n");
        string strNum;
        cin>>strNum;
        ss<<strNum;
        int a;
        ss>>a;
        a=a+1;
        cout<<a<<endl;  //NO PROBLEM HERE
    
    
        //int to String
    /* ******************************************* */
        printf("SECOND TEST\n");
        int num;
        cin>>num;
        ss<<num;
        string str;
        ss>>str;
        str=str+" IS A NUMBER";
        cout<<str<<endl;   //PROBLEM: it just print "IS A NUMBER"
    
    
     /* ****************************************** */
        printf("THIRD TEST\n");
        stringstream ss_2;  string str_2;
        cin>>num;
        ss_2<<num;
        ss_2>>str_2;
        str_2=str_2+" IS A NUMBER";
        cout<<str_2<<endl;   //NORMAL AGAIN: it will print: "<num> IS A NUMBER"
        /* ****************** */
        return 0;
    }
    //Note: PROBLEM mean I don't want like that, not something's wrong

    Uhm, in above code, at second test, if I use ss stringstream again, ss>>str will not put flow in ss into str. and the problem will be solved if I use another variable(example: ss_2). So, who can explain for me please

    thanks

  2. #2
    Registered User
    Join Date
    May 2011
    Location
    Around 8.3 light-minutes from the Sun
    Posts
    1,866
    Try this:
    Code:
    #include <iostream>
    #include <sstream>
    
    int main(void){
    
    	int num;
    	std::stringstream ss;
    	std::string output;
    
    	std::cout << "Enter a number: "; //note NO PRINTF
    	std::cin >> num;
    
    	ss << num; //place num into stringstream
    	ss >> output; //place contents of stringstream into string object
    
    	output += " is a number"; //append string object
    	std::cout << output << std::endl;
    
    	return(0);
    }
    Quote Originally Posted by anduril462 View Post
    Now, please, for the love of all things good and holy, think about what you're doing! Don't just run around willy-nilly, coding like a drunk two-year-old....
    Quote Originally Posted by quzah View Post
    ..... Just don't be surprised when I say you aren't using standard C anymore, and as such,are off in your own little universe that I will completely disregard.
    Warning: Some or all of my posted code may be non-standard and as such should not be used and in no case looked at.

  3. #3
    hqt
    hqt is offline
    Registered User
    Join Date
    Aug 2011
    Posts
    115
    yes, I have tried it, But It meets same problem with me . this is my code, building from your code:
    Code:
    int main(){
    int num;
        stringstream ss;
        string output;
        cout<<"Enter a number:";
        cin>>num;
        ss<<num;
        ss>>output;
        output+=" is a number";
        cout<<output<<endl;
    
    
    
        /* ********************** */
        cout<<"Enter a number again:";
        cin>>num;
        ss<<num;
        ss>>output;
        output+=" is a number";
        return(0);
    }

  4. #4
    Registered User
    Join Date
    Jun 2005
    Posts
    6,646
    If you want to reuse the stream then, before the line "ss << num;", you need a line "ss.clear();"
    hqt likes this.
    Right 98% of the time, and don't care about the other 3%.

    If I seem grumpy or unhelpful in reply to you, or tell you you need to demonstrate more effort before you can expect help, it is likely you deserve it. Suck it up, Sunshine, and read this, this, and this before posting again.

  5. #5
    Super Moderator VirtualAce's Avatar
    Join Date
    Aug 2001
    Posts
    9,598
    So, who can explain for me please
    I would but I cannot understand your post.

  6. #6
    Registered User gardhr's Avatar
    Join Date
    Apr 2011
    Posts
    151
    Just FYI, template functions can make arbitrary conversions fairly trivial:

    Code:
    #include <sstream>
    #include <cctype>
    #include <typeinfo>
    
    template <typename Dst, typename Src>
    bool iocpy(Dst& dst, const Src& src)
    {
    	bool success = true;
    	std::stringstream io;
    	if(!(io << src) || !(io >> dst))
    		success = false;
    	else
    	{
    		char ch;
    		while(io.get(ch))
    			if(!std::isspace(ch))
    				success = false;
    	}
    	if(!success)
    		dst = Dst();
    	return success;
    }
    
    template <typename Dst, typename Src>
    Dst iocpy(const Src& src)
    {
    	Dst dst;
    	if(!iocpy(dst, src))
    		throw std::bad_cast();
    	return dst;
    }
    
    #include <iostream>
    
    int main(int argc, char** argv)
    {
    	using namespace std;
    	int sum = 0;
    	for(int a = 1; a < argc; ++a)
    	{
    		try
    		{
    			sum += iocpy<int>(argv[a]);
    		}
    		catch(bad_cast&)
    		{	
    			cout << "Sorry, '" << argv[a] << "' is not an integer!" << endl;
    		}			
    	}	
    	cout << "Sum: " << sum << endl;
    }

  7. #7
    C++ Witch laserlight's Avatar
    Join Date
    Oct 2003
    Location
    Singapore
    Posts
    22,271
    Quote Originally Posted by gardhr
    Just FYI, template functions can make arbitrary conversions fairly trivial:
    If you have Boost, I suggest using boost::lexical_cast, though it is less tolerant of whitespace. Incidentally, the first function template could also have been written as:
    Code:
    template <typename Dst, typename Src>
    bool iocpy(Dst& dst, const Src& src)
    {
        std::stringstream io;
        bool success = (io << src) && (io >> dst >> std::ws) && io.eof();
        if (!success)
        {
            dst = Dst();
        }
        return success;
    }
    gardhr likes this.
    C + C++ Compiler: MinGW port of GCC
    Version Control System: Bazaar

    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  8. #8
    hqt
    hqt is offline
    Registered User
    Join Date
    Aug 2011
    Posts
    115
    I have use ss.clear() and nothing happened,yet.
    @ laserlight and gardhg: I'm still reading your posts (because It's may strange for me, so I will read slowly), but can you give me STD library C++ solution, please. Because, I just can use it.(for contest purpose).
    Of course, many solutions get, many ways to improve my knowledge

    thanks
    Last edited by hqt; 09-18-2011 at 02:43 AM.

  9. #9
    Registered User
    Join Date
    Jun 2005
    Posts
    6,646
    <sigh> It would also help if, in your last code fragment (post 3), you actually write output to std::cout so you can see what is happening. Writing to an object named "output" does not magically ensure anything is written to a file, cout, etc.

    I am assuming that you have recompiled and linked your code, so you are actually executing it .....
    Right 98% of the time, and don't care about the other 3%.

    If I seem grumpy or unhelpful in reply to you, or tell you you need to demonstrate more effort before you can expect help, it is likely you deserve it. Suck it up, Sunshine, and read this, this, and this before posting again.

  10. #10
    hqt
    hqt is offline
    Registered User
    Join Date
    Aug 2011
    Posts
    115
    @grumpy: your answer maybe useless to me, until I read my code again, and, :"> I haven't printed <string>output to monitor,yet.
    And after that, I see that ss.clear() have solve my question completely.(at post 1 and post 3, too)

    Again, I'm sorry sorry so much for my fault

  11. #11
    C++ Witch laserlight's Avatar
    Join Date
    Oct 2003
    Location
    Singapore
    Posts
    22,271
    By the way, one side effect of wrapping the conversion code in a function (template) is that the stringstream is used once for the conversion. This might be a little wasteful, but it means that you do not need to clear the state of the stream and reset it with an empty string in order to reuse the stringstream.
    C + C++ Compiler: MinGW port of GCC
    Version Control System: Bazaar

    Look up a C++ Reference and learn How To Ask Questions The Smart Way

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. stringstream fun
    By Prediluted in forum C++ Programming
    Replies: 2
    Last Post: 06-17-2011, 11:14 AM
  2. stringstream help
    By Airick92 in forum C++ Programming
    Replies: 6
    Last Post: 04-02-2011, 11:28 AM
  3. stringstream Help...
    By neogst in forum C++ Programming
    Replies: 4
    Last Post: 02-08-2011, 10:23 AM
  4. stringstream
    By jk1998 in forum C++ Programming
    Replies: 2
    Last Post: 07-27-2007, 07:35 PM
  5. std::stringstream
    By Magos in forum C++ Programming
    Replies: 2
    Last Post: 11-13-2004, 05:56 AM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21