Re: [boost] Re: Boost Array Initialization Technique

From: Rob Stewart (stewart_at_[hidden])
Date: 2005-06-02 11:17:22

From: "Alisdair Meredith" <alisdair.meredith_at_[hidden]>
> Rob Stewart wrote:
> 
> > I fail to see how relying on behavior of the language is not
> > having sympathy for those reading the code.  This is akin to
> > explicitly invoking a default base ctor in an initializer list in
> > my mind.
> 
> Explicit is good.

Sometimes.

> Consistent is also good.

Unless it isn't.  (I *am* a big fan of consistency but, "A
foolish consistency is the hobgoblin of little minds," as Emerson
put it.)

> Consider:
> 
> struct base
> {
>   double a;
> };
> 
> struct derived1 : base
> {
>   derived1() : base() {}
> };

I'd never invoke the default constructor of what was supposed to
be POD.  Indeed, doing so invokes default-initialization which is
counter to the norm.  Thus, not invoking the default ctor in the
initializer list is better as I was making the case for
previously.

> struct derived2 : base
> {
>   derived2() {}
> };
> 
> Which of the 2 derived classes do you think is more subtle?  derived1,
> which initialized base so member a == 0.0, or derived2 which does not
> initialize base, so a could be anything including a troublesome NaN.

The former.  It requires one to realize that it is invoking
default-initialization and it "uglifies" the initializer list
with the invocation of a default constructor.  However, I don't
care for the latter either.

> Which would you rather call attention to by breaking with convention?

Neither.  I'd write this:

struct derived3 : base
{
   derived3() { a = 0.0; }
};

> And how many 'typical' C++ programmers do you believe are even aware of
> the difference?

Few.  Thus, derived3 is superior.

> Relying (un-necessarily) on subtlety in the language, and trying to
> second guess whether it was intended or not, is generally a hard way to
> share code and an invitation for trouble in a shared-source environment.

static initialization is hardly a subtlety of the language.

> This thread is also heading off topic for a Boost list and would be
> more at home in comp.lang.c++.moderated.

Reasonable.

-- 
Rob Stewart                           stewart_at_[hidden]
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;