problems with Overloading operators

[Yudan YI \(OSU\)]

Hi
I have a problem with the overloading operators. My code is followed

header file
class TObsData
{
public:
string stnname_
double obs_;
~TObsData() {};
TObsData();
TObsData(const TObsData& obsDataSrc);
TObsData& operator= (const TObsData& obsDataSrc);
friend ostream& operator<<(ostream& os, const TObsData& obsDataSrc);
TObsSD operator- (const TObsData& obsDataSrc); // <= I want to
define an operator - and the result is another
// object of 2nd class defined later
...
}

class TObsSD
{
public:
TObsData obs_[2]; // the class contain the definition for the 1st
class
...
}


then i define the overload operator- for the TObsData class in the *.cpp
file

TObsSD TObsData:perator- (const TObsData& obsDataSrc)
{
TObsSD obsSD;
obsSD.obs_[0] = *this;
obsSD.obs_[1] = obsDataSrc;
return (obsSD);
}


a error will shown at "TObsSD operator- (const TObsData& obsDataSrc); "
when I try to complie the project

do you guy know what cause this problem?

Thanks
Yudan

 

[Raymond Martineau]

Hi
I have a problem with the overloading operators. My code is followed

header file
class TObsData
{
public:
string stnname_
double obs_;
~TObsData() {};
TObsData();
TObsData(const TObsData& obsDataSrc);
TObsData& operator= (const TObsData& obsDataSrc);
friend ostream& operator<<(ostream& os, const TObsData& obsDataSrc);
TObsSD operator- (const TObsData& obsDataSrc); // <= I want to
define an operator - and the result is another

This is one reason to avoid "//" comments while posting on usenet. Some
news-readers will perform word-wrap and introduce unexpected errors.

// object of 2nd class defined later

The error occurrs because class TObsSD isn't yet defined.

You need to put a forward declaration. For example:

class TObsSD;

class TObsData
{

 

[Yudan YI \(OSU\)]

But, the problem is that I want to use the 1st class in my 2nd class. if I
put the 2nd class definition, it still will have problem. Any good apprach
to fix it?
Thanks

 

[Yudan YI \(OSU\)]

Thanks, you method works
Yudan

This is one reason to avoid "//" comments while posting on usenet. Some
news-readers will perform word-wrap and introduce unexpected errors.


The error occurrs because class TObsSD isn't yet defined.

You need to put a forward declaration. For example:

class TObsSD;

class TObsData
{

 

[Ole Reinartz]

But, the problem is that I want to use the 1st class in my 2nd class. if I
put the 2nd class definition, it still will have problem. Any good apprach
to fix it?
Thanks

Maybe you can make operator - to return a reference to const? Like
const TObsSD& operator- (const TObsData& obsDataSrc) const;

Then you might get away forward declaring TObsSD. Your reference will
most probably point to a temporary (it should, at least), but AFAIR it
is mentioned somewhere in the standard that the temporary must not be
destroyed while a reference exists that points to it. What was the
clause again?

A yes, and your opreator shuold be const. It shouldn't really change its
operands, right?

Ole