Thread: 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.

Did the code you posted compile?

Code:

istream& operator >> (ostream &is, coord &c)
// should be
istream& operator >> (istream &is, coord &c)

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.

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.

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.

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

Thanks, guys. That's just the help I needed. My first class is now complete. Yay!

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.

It'd probably help if I included the file, huh? Well, here it is: