Error returning istream in class implementation.

This is a discussion on Error returning istream in class implementation. within the C++ Programming forums, part of the General Programming Boards category; I'm working on a class called coord that's just two dimensional coordinates. The only data members are the x-coordinate and ...

  1. #1
    Senior Member joshdick's Avatar
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    Error returning istream in class implementation.

    I'm working on a class called coord that's just two dimensional coordinates. The only data members are the x-coordinate and the y-coordinate. I wrote a function to input a coord like so, but the compiler is giving me this error:
    Code:
    	is >> char1 >> X >> char2 >> Y >> char3;
                        ^
    File "Hard Drive:Desktop Folder:Comp Prgms:My RPG:coord.cpp"; line 108
    #Error: ambiguous type conversion
    Had: ios::operator const void*() const
    and: ios::operator void*()
    I don't know what the problem is. I followed the same format to implement this function as my textbook used to implement a rational number class. Here's the implementation of my input function:
    Code:
    istream& operator >> (ostream &is, coord &c)
    {
    	char char1, char2, char3;
    	int X = 0, Y = 0;
    	is >> char1 >> X >> char2 >> Y >> char3;
    	assert(char1 == '(');
    	assert(char2 == ',');
    	assert(char3 == ')');
    	coord pair(X,Y);
    	c = pair;
    	return is;
    }
    Any help will be much appreciated. This is my first class that I have written, and I think this is the last bug in it *crosses fingers*. Thanks in advance.
    FAQ

    "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum.

    "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.

  2. #2
    geek SilentStrike's Avatar
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    Did the code you posted compile?

    Code:
    istream& operator >> (ostream &is, coord &c)
    // should be
    istream& operator >> (istream &is, coord &c)
    Prove you can code in C++ or C# at TopCoder, referrer rrenaud
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  3. #3
    Senior Member joshdick's Avatar
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    Originally posted by SilentStrike
    Code:
    istream& operator >> (ostream &is, coord &c)
    // should be
    istream& operator >> (istream &is, coord &c)
    Oh, my god, I feel so stupid. *hangs head in shame* I can't believe I made such a silly little mistake. Thanks, man, now it compiles just fine.
    FAQ

    "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum.

    "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.

  4. #4
    Senior Member joshdick's Avatar
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    Question Another question about my coord class

    How do I assign an ordered pair to a coord? Here's what I'd like to be able to do:
    Code:
    coord ordered_pair;
    ordered_pair = (1,2);
    I know I can already do this:
    Code:
    coord ordered_pair(1,2);
    but, that only works when I first declare the variable. After that, I'm unable to assign to a coord in that manner. I think that all I'll need to fix this problem is the function declaration for the assignment I want. Once again, thanks in advance.
    FAQ

    "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum.

    "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.

  5. #5
    geek SilentStrike's Avatar
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    You would need to alter the langauge to allow things like this to do what you want.
    Code:
    ordered_pair = (1,2);
    That will basically evulate the statement 1 first, and then evaulate and return 2. Run the following code in case you are confused.

    Code:
    #include <iostream>
    
    int f() {
      std::cout << "f()\n";
      return 1;
    }
    
    int g() {
      std::cout << "g()\n";
      return 2;
    }
    
    int main()
    {
      int b = (f(),g());
      std::cout << b << std::endl;
      return 0;
      
    }
    You can either make a member, set_coords or soemthing, that takes two parameters, or use the the constructor and assignment. IE,

    Code:
    order_pair = coord(a,b);
    // or
    order_pair.set_coords(a,b)
    The second way is likely to be minimally faster.
    Prove you can code in C++ or C# at TopCoder, referrer rrenaud
    Read my livejournal

  6. #6
    Programming Sex-God Polymorphic OOP's Avatar
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    you could always overload operator() to take 2 values so that you could do this:

    ordered_pair( Newx, Newy );

    but that would most likely just be confusing. Best off just using a "Set" method

  7. #7
    Senior Member joshdick's Avatar
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    Thanks, guys. That's just the help I needed. My first class is now complete. Yay!
    FAQ

    "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum.

    "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.

  8. #8
    Senior Member joshdick's Avatar
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    My coord class is done and tested. I'd now like to make it available to you for criticism and suggestions. I've included a library driver to test the code. Just so you know, my only current plans for this class is to track the location of the player in a text based RPG (I know, not much fun, but I've got to start somewhere). Thanks in advance.
    FAQ

    "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum.

    "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.

  9. #9
    Senior Member joshdick's Avatar
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    It'd probably help if I included the file, huh? Well, here it is:
    FAQ

    "The computer programmer is a creator of universes for which he alone is responsible. Universes of virtually unlimited complexity can be created in the form of computer programs." -- Joseph Weizenbaum.

    "If you cannot grok the overall structure of a program while taking a shower, you are not ready to code it." -- Richard Pattis.

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