[boost] Re: A better CopyPtr

From: Kevlin Henney (kevlin_at_[hidden])
Date: 2000-03-07 03:33:33

In message <Pine.LNX.4.10.10003061513200.6848-100000_at_kevins-linux>,
Kevin Atkinson <kevinatk_at_[hidden]> writes
>
>>   template <typename T>
>>   CopyPtr<T> & CopyPtr<T>::operator= (const CopyPtr<T> & other) 
>>   {
>>     delete ptr;
>>     if (other.ptr != 0) 
>>       ptr = new T(*other.ptr);
>>     else
>>       ptr = 0;
>>     return *this;
>>   }
>
>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) { 
>      if (other.ptr == 0) 
>        ptr = 0; 
>      else  
>        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;
        }
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  Kevlin Henney                 Without art we are nothing
  kevlin_at_[hidden]                but monkeys with car keys
  kevlin_at_[hidden]
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