Ambiguous operator[]

This is a discussion on Ambiguous operator[] within the C++ Programming forums, part of the General Programming Boards category; I have a class with an overloaded [] operator, as follows: Code: char & STRING::operator[] (unsigned); char STRING::operator[] (unsigned) const; ...

  1. #1
    Registered User MacNilly's Avatar
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    Ambiguous operator[]

    I have a class with an overloaded [] operator, as follows:

    Code:
    char & STRING::operator[] (unsigned);
    char STRING::operator[] (unsigned) const;
    The class also has a char*() operator, as follows:

    Code:
    STRING::operator char* ();
    The problem is, when I try a some code such as:
    Code:
    STRING a;
    a[0] = 'A';
    I get a compiler error saying that this operator[] call is ambiguous, that it can't decide between my STRING:perator[] and the built-in operator[] that works for char pointers. So far the only thing I can think of is that the compiler is implicitly casting my STRING to a char * using my operator char*() function. The only way this code works is if I comment out the prototype for operator char*. Unfortunately, I need to have that function working. Any help out there for me?
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  2. #2
    Cat without Hat CornedBee's Avatar
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    Remove the conversion operator. Supply a function similar to std::string::c_str() instead. A conversion to char* is way more trouble than it is ever worth.
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  3. #3
    The larch
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    You can be more specific when using the [] operator:
    Code:
    a.operator[](0) = 'A';
    But a better solution might be to give up the conversion overload and just use a member function to get the char*.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
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  4. #4
    Registered User MacNilly's Avatar
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    Thanks for the replies. I will implement it as a member function similar to string::c_str(). I guess I will have to tell the teacher that his prototypes are not going to work with one another.
    GCC on Fedora Core 10

  5. #5
    Algorithm Dissector iMalc's Avatar
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    Quote Originally Posted by CornedBee View Post
    Remove the conversion operator. Supply a function similar to std::string::c_str() instead. A conversion to char* is way more trouble than it is ever worth.
    QFE, although I see you've already taken this advice.

    Don't worry, everyone who ever tries to write their own string class seems to think that they can make it easier or more convenient to use than std::string, only to discover that std::string pretty much is the best the language can offer us. There is a reason for everything.
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  6. #6
    C++ Witch laserlight's Avatar
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    Don't worry, everyone who ever tries to write their own string class seems to think that they can make it easier or more convenient to use than std::string, only to discover that std::string pretty much is the best the language can offer us.
    std::string is not the best that the language (or standard library, rather) could have offered us. For example, it is a classic example of a monolithic class.
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