sprintf equivalence in C++

This is a discussion on sprintf equivalence in C++ within the C++ Programming forums, part of the General Programming Boards category; Hi, I was getting some help at the C forum, on converting an int to a char[]. Quzah suggested the ...

  1. #1
    Microsoft. Who? MethodMan's Avatar
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    sprintf equivalence in C++

    Hi,

    I was getting some help at the C forum, on converting an int to a char[]. Quzah suggested the use of sprintf, but now I have decided to implement what I am doing in C++, rather than C, and I am getting compilation errors with sprintf.

    Is there an equivalent function of sprint in C++? or is there another way to approach the conversion.


    I wasnt sure if I should get the post moved, a mod can merge them if they feel they should be.

    Thanks.
    -MethodMan-

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    Quote Originally Posted by MethodMan
    Hi,

    I was getting some help at the C forum, on converting an int to a char[]. Quzah suggested the use of sprintf, but now I have decided to implement what I am doing in C++, rather than C, and I am getting compilation errors with sprintf.

    Is there an equivalent function of sprint in C++? or is there another way to approach the conversion.


    I wasnt sure if I should get the post moved, a mod can merge them if they feel they should be.

    Thanks.
    sprintf() is available in C++. Try this:
    Code:
    #include <iostream>
    
    using namespace std
    
    int main()
    {
      char *temp="Hello";
      char temp2[100];
      sprintf(temp2, "%s World", temp);
      cout << "temp: <" << temp << ">" << endl;
      cout << "temp2: <" << temp2 << ">" << endl;
    
      return 0;
    }
    If it doesn't work, post your compiler errors


    Regards,

    Dave

  3. #3
    Registered User hk_mp5kpdw's Avatar
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    If you decide not to use sprintf, the "other way to approach the conversion" is to use stringstreams:

    Code:
    #include <iostream>
    #include <strstream>
    using namespace std;
    
    int main()
    {
        strstream temp;
        int data = 15;
        char buffer[20];
    
        temp << data;     // Store int in strstream
        temp >> buffer;   // Read int value back into char buffer
    
        cout << buffer << endl;
    
        return 0;
    }

    Or...

    Code:
    #include <iostream>
    #include <sstream>
    #include <string>
    using namespace std;
    
    int main()
    {
        stringstream temp;
        int data = 15;
        string buffer;
    
        temp << data;     // Store int in stringstream
        temp >> buffer;   // Read int value back into string
    
        cout << buffer << endl;
    
        return 0;
    }
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
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  4. #4
    Microsoft. Who? MethodMan's Avatar
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    Im getting a cast error, I must be calling sprintf() wrong

    //funtion prototype
    void Timer:rawText(GLint x, GLint y, char* s, GLfloat r, GLfloat g, GLfloat b);

    int i = 10; // want that to be used in my function, need to convert it
    char buf[256];

    sprintf(buf, sizeof(buf), i);

    And then I would use buf in my function call.

    Edit:

    strstream' : undeclared identifier

    I included the header file, but I get the following error....

    Im using Visual Studio
    Last edited by MethodMan; 11-21-2004 at 06:31 PM.
    -MethodMan-

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  5. #5
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    Quote Originally Posted by MethodMan
    Im getting a cast error, I must be calling sprintf() wrong


    int i = 10; // want that to be used in my function, need to convert it
    char buf[256];

    sprintf(buf, sizeof(buf), i);
    Well, you are correct: that is wrong. You need a format specifier, like in printf().

    If you already had sprintf() working in C, I think you could use in C++ exactly the same way as you did.

    Given your present status, I see two possibilities:

    1. Learn to use sprintf().

    2. Learn to use stringstreams.

    If you are going to use C++, maybe your time would be better spent learning about stringstreams, as was suggested by hk_mp5kpdw.

    Regards,

    Dave

  6. #6
    Toaster Zach L.'s Avatar
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    Yeah, you don't need the size, and you do need a format specifier. Here is a link: http://cppreference.com/stdio_details.html#sprintf

    I really would recommend stringstreams with strings, though (hk_mp5kpdw's second example). That is a much less error prone solution.
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  7. #7
    carry on JaWiB's Avatar
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    Wouldn't it be better to use the ostringstream class? I think strstream is deprecated
    Code:
    #include <iostream>
    #include <sstream>
    using namespace std;
    
    int main()
    {
        ostringstream temp;
        int data = 15;
        char buffer[20];
    
        temp << data << flush;     // Store int into stream
        temp.str().copy(buffer, 20);   // Read int value back into char buffer
        cout << buffer << endl;
        cin.get();
        return 0;
    }
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  8. #8
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    Using your example:
    Code:
    int i = 10; // want that to be used in my function, need to convert it
    char buf[256];
    
    sprintf(buf, "%d", i);
    It works the same as printf(), just outputs to a string versus the screen.

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