On 04/03/2012 10:27 AM, Don Clugston wrote:
On 03/04/12 07:38, Nick Sabalausky wrote:
Regarding this:
http://d.puremagic.com/issues/show_bug.cgi?id=790
I submit that nested functions should be exempt from the usual sequential
visibility rules. (Therefore, mutually recursive nested functions would
become possible.)
Or at the very *least*, this horrific C-like workaround should be
possible:
void foo()
{
void b();
void a() {...};
void b() {...};
}
...Flame away! ;)
This is asking for a complicated special case. In global scope, order of
declarations doesn't matter. In function scope, order of declarations
always matters.
If you have type inference of function returns, things can get nasty:
void foo()
{
auto b() { return a(); }
X x = whatever;
auto a() { return x; }
}
Now b actually depends on the declaration of x. So it's not enough to
say that only function declarations are immune to ordering rules.
I come to a different conclusion. If only function declarations are
immune to ordering rules, the above example is simply illegal. The
example cannot be used to demonstrate incompleteness of the approach.
Furthermore, any declaration before x, which calls b(), is using x even
though x hasn't been initialized (or even declared) yet. Suddenly all
kinds of horrible situations become possible, which could never happen
before.
In general, allowing forward references inside a function is far, far
more difficult than in global scope.
If it is constrained enough, it shouldn't be more difficult.
There are very many more special
cases. Allowing it in global scope is quite complicated enough.
It should be possible to leverage the efforts spent there.
You can always use a delegate, if you want recursive nested functions.
Templates are superior.
