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Michael T. Peterson
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 Posted: Sun Aug 29, 2004 11:42 pm Post subject: [Q] HOWTO overload '==' operator? |
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I am unable to figure out how to overload the '==' operator. The code
below( cc'd it from an example on the net) doesn't compile:
bool operator== ( const GivenName &lhs, const GivenName &rhs ) {
return( lhs.first == rhs.first && lhs.middle == rhs.middle &&
lhs.last == rhs.last );
}
The error message is 'operator ==' has too many parameters.
Any suggestions, explanations, references to docs or books, etc., would be
greatly appreciated.
Cheers,
Michael
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David Hilsee
Guest
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| Posted: Sun Aug 29, 2004 11:50 pm Post subject: Re: [Q] HOWTO overload '==' operator? |
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"Michael T. Peterson" <mtp1032 (AT) comcast (DOT) net> wrote
| Quote: | I am unable to figure out how to overload the '==' operator. The code
below( cc'd it from an example on the net) doesn't compile:
bool operator== ( const GivenName &lhs, const GivenName &rhs ) {
return( lhs.first == rhs.first && lhs.middle == rhs.middle &&
lhs.last == rhs.last );
}
The error message is 'operator ==' has too many parameters.
Any suggestions, explanations, references to docs or books, etc., would be
greatly appreciated.
|
It sounds like you made that function a member. As it is currently written,
it should not be a member function. Example:
class GivenName {
// members first, middle, last, etc
friend bool operator== ( const GivenName &lhs, const GivenName &rhs ) {
return lhs.first == rhs.first && lhs.middle == rhs.middle &&
lhs.last == rhs.last;
}
};
--
David Hilsee
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Victor Bazarov
Guest
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| Posted: Mon Aug 30, 2004 1:00 am Post subject: Re: [Q] HOWTO overload '==' operator? |
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"Michael T. Peterson" <mtp1032 (AT) comcast (DOT) net> wrote...
| Quote: | I am unable to figure out how to overload the '==' operator. The code
below( cc'd it from an example on the net) doesn't compile:
bool operator== ( const GivenName &lhs, const GivenName &rhs ) {
return( lhs.first == rhs.first && lhs.middle == rhs.middle &&
lhs.last == rhs.last );
}
The error message is 'operator ==' has too many parameters.
Any suggestions, explanations, references to docs or books, etc., would be
greatly appreciated.
|
Take a good look at the example from which you cc'd your code. Was the
operator== there a member or was it a stand-alone function? Did you make
it a member? Now, analyse the difference. Why in the example on the net
it worked, and in your code it doesn't? What book on C++ are you reading
at this time? Does it talk about operator overloading at all? If it does
talk about it, have you paid attention to the difference between member/
non-member operators, especially to the number of their arguments?
Victor
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Thomas Matthews
Guest
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| Posted: Mon Aug 30, 2004 2:13 pm Post subject: Re: [Q] HOWTO overload '==' operator? |
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Michael T. Peterson wrote:
| Quote: | I am unable to figure out how to overload the '==' operator. The code
below( cc'd it from an example on the net) doesn't compile:
bool operator== ( const GivenName &lhs, const GivenName &rhs ) {
return( lhs.first == rhs.first && lhs.middle == rhs.middle &&
lhs.last == rhs.last );
}
The error message is 'operator ==' has too many parameters.
Any suggestions, explanations, references to docs or books, etc., would be
greatly appreciated.
Cheers,
Michael
|
As a member function of a class:
class Bicycle
{
public:
bool operator==(const Bicycle& b) const;
};
In your case (perhaps, as you haven't supplied much
to work with):
class PersonName
{
public:
bool operator==(const PersonName & pn) const;
private:
std::string first;
std::string middle;
std::string last;
};
bool
PersonName ::
operator==(const PersonName& pn) const
{
return (last == pn.last)
&& (first == pn.first)
&& (middle == pn.middle);
}
--
Thomas Matthews
C++ newsgroup welcome message:
http://www.slack.net/~shiva/welcome.txt
C++ Faq: http://www.parashift.com/c++-faq-lite
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http://www.comeaucomputing.com/learn/faq/
Other sites:
http://www.josuttis.com -- C++ STL Library book
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Michael T. Peterson
Guest
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| Posted: Mon Aug 30, 2004 2:41 pm Post subject: Re: [Q] HOWTO overload '==' operator? |
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Thanks, everyone. all of your insights haven proven very helpful.
Cheers,
Michael
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