🚀 go-pugleaf

I hope I don't sound like I'm second-guessing people who are likely much more
experienced than I am in library design, but I have another question about
auto_ptrs.

Specifically, the (April '95) draft standard auto_ptr doesn't have an operator
bool() function in it, making it inconvenient to write "if (ptr)" type
constructs. Is there some sort of reason for that? I know that implicit type
conversion is generally a bad thing, but I can't see how this one would be
particularly dangerous (also, can the new explicit keyword be used on the
return type?).

Now, Meyers's latest book describes an auto_ptr that has member templates, so
obviously the April WP does not have the latest auto_ptr, but I get the
impression even the current auto_ptr doesn't have an operator bool(). My
reading of Meyers's discussion of smart_ptrs mentions that operator bool()
would allow comparison of two different types of auto_ptrs, but the latest
iostream standard has an operator bool() and an operator!() defined. So why not
be consistent?

In fact, as another idea, what about defining a new class, say, explicit_bool?
explicit_bool would have an operator bool() defined, but would also have an
operator==(const explicit_bool &rhs) and operator!=(const explicit_bool &rhs)
defined as a private function. It would also have operator!() return an
explicit_bool. This way, constructs such as "if (myptr)" and "if (!myptr)"
would work, but "if (myptr==otherptr)" and "if (myptr != otherptr)" wouldn't
compile.

Just a thought, anyway. I'm sure there are holes in that idea.



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