a+b+c is not equal to a+(b+c)

[Adrian]

Why would that be better? I thought the result would be the same? That is,
operator+(a,b) is the same as a+b.

Becuase that way you can write
1. a+5
2. 5+a
3. a+b

If operator+ is a friend a Bigint will automatically be constructed for
1 and 2 if needed. As a member function option 2 isn't possible


Adrian

 

[Peter Koch Larsen]

Why would that be better? I thought the result would be the same? That is,
operator+(a,b) is the same as a+b.

You should in BigInt have an operator:

BigInt& operator+=(BigInt const& rhs);

and the same for -=, *= and /=.

Now the "standard" operators become very simple to write:

BigInt operator+(BigInt lhs,BigInt const& rhs)
{
return lhs+=rhs;
}

The same principle is used for the other operators.

Kind regards
Peter

 

[Howard]

[..]
Is there anyplace that lists which operators should be friends and which
should be members? I always seem to end up looking at existing code
someplace else when trying to decide, and that's a big waste of time.

IIRC, it's called "Effective C++". Probably, Item 19. Don't have my copy
here, sorry.

Victor

Ok, I've re-read that section now. Still, I have trouble remembering it. I
was kind of hoping for a little chart for operators (only). I suppose I can
make one myself...

-Howard

 

[Victor Bazarov]

[..]
Is there anyplace that lists which operators should be friends and which
should be members? I always seem to end up looking at existing code
someplace else when trying to decide, and that's a big waste of time.

IIRC, it's called "Effective C++". Probably, Item 19. Don't have my copy
here, sorry.

Victor

Ok, I've re-read that section now. Still, I have trouble remembering it. I
was kind of hoping for a little chart for operators (only). I suppose I can
make one myself...

It's not a bad idea. You'll learn it better while making it than if
somebody else makes one and you just read it.

V