Re: [boost] Re: Pretty Good Initialization Library

From: Jon Kalb (jonkalb_at_[hidden])
Date: 2004-07-12 11:53:10

On 7/10/04 12:32 PM, "Andrei Alexandrescu (See Website for Email)"
<andrewalex_at_[hidden]> wrote:

> For the record, I've decided to eliminate that coding standard

   on overloading operator,()

> for now. The
> sheer facts that (1) a useful library overloading operator,() is in boost,
> and (2) reasonable people can disagree about said overloading being good or
> bad, convinced me.

I'm disappointed in this. While there may be identifiable exception cases, I
think in general overloading operator,() is problematic. I think the
initialization library's use of the comma operator in this way is like the
streams use of >> and <<. These are really new operators which happen to be
spelled the same way as old operators.

When we see "std::cout << ...", we don't think, "Oh, this is bit shift which
in the case of streams means..." No we think "Oh, this is the insertion
operator..."

I think of the comma operator as the sequence operator and as such it cannot
be properly overloaded. To overload operator,() in the way that the
initialization library does is to introduce a new operator in much the same
way that the stream class did with << and >>.

Perhaps the coding guideline should be "overload operator,() only when you
wish to create a new semantic meaning for the comma operator (other than
sequence) and see the coding guideline that says to avoid creating new
semantic meanings for operators."

-- 
Jon Kalb