Re: Explicit call to constrcutors
* Prasoon:
Can constructors be explicitly called in a program with using
placement new???
The question implies some confusion about what "explicit" means.
Look up the words "explicit" and "implicit" in your nearest dictionary.
As far as I know....considering the code snippet
#include<iostream>
class demo
{
public:
demo(){
std::cout<<"Constructor invoked";
}
~demo(){
std::cout<<"Destructor invoked";
}
};
int main()
{
demo d;//Constructor invoked
d.demo();//Compilation error
demo();//Creation of nameless object
d.~demo();//Allowed but may lead to undefined behaviour as the
local object
//d can be destructed twice
}
Is the creation of nameless object in the above code an explicit call
to constructor or not???
Is it explicit? Yes. Is it a constructor call? Yes.
According to me,its not.
You can define your own terminology, of course, e.g. that when you refer to a
"car" you mean a little a flying insect.
And in some cases it's a good idea to not succumb to standardeese, e.g. in
common speak we just say "promotion" when in standardeese we'd have to say
"usual arithmetic conversion", and to top it off "promotion" means something
different, more limited and specialized, in standardeese.
But for most terms the standard's usage (and in this case also the usage of the
language's creator Bjarne Stroustrup) is all fine, it's just the usual normal
meaning!, so it's very counter-productive to adopt any other meaning.
To call a constructor explicitly we need to
use Placement new but again it is not recommended to use "Placement
New"
Placement new has nothing to do with the explicitness of your code.
You are confused about the word "explicit".
Look up the words "explicit" and "implicit" in your nearest dictionary.
Is there any other way of calling constructors explicitly????
You have an explicit call when you do it explicitly, i.e. when you supply an
argument list (which may be empty).
Cheers & hth.,
- Alf
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