returning a string?

This is a discussion on returning a string? within the C++ Programming forums, part of the General Programming Boards category; I've basically been playing with C++ more and more recently and one thing i've came accross is returning a string? ...

  1. #1
    PPN
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    returning a string?

    I've basically been playing with C++ more and more recently and one thing i've came accross is returning a string?

    I tried to declare it in my header file while doing the prototypes and the VS .NET doesn't seem to like it, it was fine when i was using char but now i need to return two characters.

    i included the string library so i'm now puzzled.

    Code:
    #include <string>
    using namespace std;
    
    string convert_num(int cnumber) {
    	string temp;
    	cnumber = (cnumber%13);
    	switch (cnumber) {
    		case 0:
    			temp = 'K';
    			break;
    		case 1:
    			temp = 'A';
    			break;
    		case 2:
    			temp = '2';
    			break;
    		case 3:
    			temp = '3';
    			break;
    		case 4:
    			temp = '4';
    			break;
    		case 5:
    			temp = '5';
    			break;
    		case 6:
    			temp = '6';
    			break;
    		case 7:
    			temp = '7';
    			break;
    		case 8:
    			temp = '8';
    			break;
    		case 9:
    			temp = '9';
    			break;
    		case 10:
    			temp = '10';
    			break;
    		case 11:
    			temp = 'J';
    			break;
    		case 12:
    			temp = 'Q';
    			break;
    		default :
    			temp = 'K';
    			break;
    	}
    	return temp;
    }
    and in the head file

    Code:
    string convert_num(int cnumber);
    and yes it is the customary blackjack game that everyone gets asked to do.

  2. #2
    Registered User hk_mp5kpdw's Avatar
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    Your string variable temp is declared locally to the function convert_num. When the function exits, any variable/objects that you declare in such a manner are effectively destroyed and therefore unavailable to any function that calls convert_num and relies upon getting a valid string object returned from it. What you need to do is either pass in an additional string parameter (by pointer/reference) and modify that object in the function, or modify the function to return a pointer to a string object that you dynamically allocate and modify within the convert_num function.
    "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."
    -Christopher Hitchens

  3. #3
    S Sang-drax's Avatar
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    Originally posted by hk_mp5kpdw
    Your string variable temp is declared locally to the function convert_num. When the function exits, any variable/objects that you declare in such a manner are effectively destroyed and therefore unavailable to any function that calls convert_num and relies upon getting a valid string object returned from it. What you need to do is either pass in an additional string parameter (by pointer/reference) and modify that object in the function, or modify the function to return a pointer to a string object that you dynamically allocate and modify within the convert_num function.
    What you're saying is very wrong. std::string doesn't work that way at all.

    The only thing he has to do is to replace the singe-quotes (') with double quotes (")
    Last edited by Sang-drax : Tomorrow at 02:21 AM. Reason: Time travelling

  4. #4
    PPN
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    c:\Documents and Settings\Administrator.SCOTT\My Documents\Visual Studio Projects\blackjack\deck.h(9): error C2146: syntax error : missing ';' before identifier 'convert_num'

    c:\Documents and Settings\Administrator.SCOTT\My Documents\Visual Studio Projects\blackjack\deck.h(9): error C2501: 'string' : missing storage-class or type specifiers
    which is the function prototype, the header file has the following

    Code:
    //
    // Scott MacVicar
    // Black Jack Game
    //
    
    void shuffle ();
    char suit (int cnumber);
    void deal (int array[10], int card);
    string convert_num (int cnumber);

  5. #5
    PPN
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    nevermind i feel stupid now

    std::string convert_num (int cnumber);

    works, silly namespaces

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