c++ strings

This is a discussion on c++ strings within the C++ Programming forums, part of the General Programming Boards category; Hello.. I've been programming for some time, but I have never been using c++ strings before.. Im not sure when ...

  1. #1
    l2u
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    c++ strings

    Hello..

    I've been programming for some time, but I have never been using c++ strings before.. Im not sure when should I use them and how? Always when I have to deal with char *? Im a little confused since im used to char *sth = new char[BUF_SIZE]; ..

    Thanks for help

  2. #2
    Carnivore ('-'v) Hunter2's Avatar
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    C++ strings:
    std::string mystring;

    Use a C++ string whenever you need store a string. As for how, google "C++ string tutorial". They're much easier to use than char*.
    Just Google It. √

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  3. #3
    l2u
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    So from now on I should do:

    Code:
    template <class t>
    class datalist {
    public:
    	datalist() { }
    	string name;
            t data;
    };
    instead of char *name.

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    you'll need to #include <string> also. Be sure to do a search for string, so you can find all the functions available for it.

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    The Richness... Richie T's Avatar
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    See this reference on string functions:

    http://www.cppreference.com/cppstring/index.html

    C++ strings are to C strings as C++ vectors are to C arrays - pretty much better in every
    way.
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  6. #6
    The superhaterodyne twomers's Avatar
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    >> C++ strings are to C strings as C++ vectors are to C arrays - pretty much better in every
    way.

    Yes indeed. All functions are associated with the strings . thing (sorry for my poorly chosen vocab), so you don't have to remember (taking examples from C), strcat, strlen etc. The + and = operators are overloaded, and there is a .size(), .find(), .c_str(), and lots of other functions with them, which IMO, makes them great.

    fast example C++ ::

    Code:
    std::string MyStringA = "this is a std::string. ";
    std::string MyStringB = "See how it Roars";
    std::string MyStringAB = MyStringA + MyStringB;
    
    std::cout<< '\n' << MyScringAB;// should be - this is a std::string. See how it Roars
    std::cout<< '\n' << MyScringAB.size(); // the size of the string, I'm not counting it :)
    obviously, if you REALLY wanted to, you could put a using namespace std;, or using std::cout; using std::string; or whatever to get rid of all those st::'s, but it's generally advised to use std::'s for large projects.

    Fast example, C: (If I can remember syntaxi etc)

    Code:
    char *MyStringA = "this is a std::string. ";
    char *MyStringB = "See how it Roars";
    char MyStringAB[100];
    
    strcpy( strcat( MyStringA, MyStringB ), MyStringAB ); 
    // can't remember whether the destination comes first or 
    // last with strcpy, nor can I remember whether they shuld be
    // char []'s, or char *'s or whether it makes a difference. 
    
    printf( "%s", MyStringAB );
    printf( "%d", strlen( MyStringAB );
    IMO, C++ way = nicer
    Last edited by twomers; 09-03-2006 at 01:56 PM.

  7. #7
    すまん Hikaru's Avatar
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    Quote Originally Posted by l2u
    Im not sure when should I use them and how?
    Always use them! C++ strings are a replacement for C strings. They're safer, easier, and can do more with less code. You can even get a C string from a C++ string with the c_str member function for any old libraries that use C strings.
    Quote Originally Posted by l2u
    Im a little confused since im used to char *sth = new char[BUF_SIZE]; ..
    It's even easier! You don't need a size because C++ strings grow automatically. You also don't need to remember to free memory because C++ strings manage memory automatically. I think those are two big problems in programming.

  8. #8
    Cat
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    As a clarification, c_str() gives a const C-style string. It's fine for any function call that reads a string, but function calls which modify or create a string will still need C-style strings.

    So the only time to use C-style strings are when you're using some function (e.g. an API call) that changes the contents of a buffer. As soon as the function call ends I make a string with the contents of the buffer and clean up the buffer.

    So, for example:

    Code:
    char * buffer = new char[neededSize];
    int bytesWritten = FillBufferFunction(buffer, neededSize); // Just some random function which fills the buffer
    std::string str(buffer, bytesWritten);
    delete[] buffer;
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  9. #9
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    Even then, it is generally better to use a vector, which deletes itself.
    Code:
    std::vector<char> buffer(neededSize);
    int bytesWritten = FillBufferFunction(&buffer[0], neededSize); // Just some random function which fills the buffer
    std::string str(buffer.begin(), buffer.begin() + bytesWritten);

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