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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.


> 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

> 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.


Rob Stewart                           stewart_at_[hidden]
Software Engineer           
Susquehanna International Group, LLP  using std::disclaimer;

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