[boost] Re: A better CopyPtr

From: Kevin Atkinson (kevinatk_at_[hidden])
Date: 2000-03-07 07:01:36

On Tue, 7 Mar 2000, Kevlin Henney wrote:

> In message <Pine.LNX.4.10.10003061513200.6848-100000_at_kevins-linux>,

> >Here is a more complicated but more efficient operator=:
> >
> >  template <typename T> 
> >  CopyPtr<T> & CopyPtr<T>::operator= (const CopyPtr<T> & other)  
> >  { 
> >    if (other.ptr == 0) { 
> >      delete ptr; 
> >      ptr = 0; 
> >    } else if (ptr == 0) { 
> >      ptr = new T(*other.ptr); 
> >    } else { 
> >      *ptr = *other.ptr; 
> >    } 
> >    return *this; 
> >  } 
> 
> And here is one that is simpler, exception safe, but only as efficient
> as the original version:
> 
>         template<typename T>
>         CopyPtr<T> & CopyPtr<T>::operator=(const CopyPtr & other)
>         {
>                 T * old = ptr;
>                 ptr = other.ptr ? new T(*other.ptr) : 0;
>                 delete old;
>                 return *this;
>         }

How is mine not exception safe?

---
Kevin Atkinson
kevinatk_at_[hidden]
http://metalab.unc.edu/kevina/