small operator question

[Kev]

As its not possible, as far as I know, to have more than one parameter in
an overloaded equality operator, is it possible to do something like this?

MyStruct A(1, 2, 3), B(4, 5, 6);

A = B; works;

A = MyStruct(4, 5, 6); does not

Thx

 

[Alf P. Steinbach]

* Kev:

As its not possible, as far as I know, to have more than one parameter in
an overloaded equality operator,

It seems you mean assignment operator.

is it possible to do something like this?

MyStruct A(1, 2, 3), B(4, 5, 6);

A = B; works;

A C++ comment can look like this:

A = B; // works

A = MyStruct(4, 5, 6); does not

In general you cannot detect that an argument is a temporary, so no, you
can not make the last construction not work except for special cases --
and why would you?

 

[Aries Sun]

"A = MyStruct(4, 5, 6); " should work, if you defined MyStruct's
constructor explicitly

Aries Sun

 

[Earl Purple]

It worked on VC7.1 even when I made the operator= take a non-const
reference:

#include <algorithm>

struct MyStruct
{
int a;
int b;
int c;
MyStruct( int x, int y, int z )
: a(x), b(y), c(z)
{
}

MyStruct& operator=( MyStruct& rhs )
{
std::swap( a, rhs.a );
std::swap( b, rhs.b );
std::swap( c, rhs.c );
return *this;
}
};

int main()
{
MyStruct A(1,2,3), B(4,5,6);
A = B;
A = MyStruct( 4, 5, 6 );
return 0;
}

 

[Kev]

It worked on VC7.1 even when I made the operator= take a non-const
reference:

I did not have my contructor set up properly. Thanks everyone!