Re: [boost] boost::nil

From: Iain.Hanson_at_[hidden]
Date: 2001-06-08 09:49:13

gregod (gregod_at_[hidden]) wrote

     snip ...
>Advantages of 'nil' over NULL:
>       - NULL is not necessarily portable. Some C++ compilers pick up bad 
>information to the user.

The problem is that there is no portable definition of nil. nil has been defined
by a bzillion different people to mean different things. Stroustrup's D & E 
discusses the problems with this. CORBA has a nil, Czarnecki & Eisenecker have  
a nil in the software from their book 'Generative Programming' and many other 
class libraries have a nil. This seems like a bad idea IMHO.

     
>Advantages of 'nil' over 0:
>       - 0 is an integer. It converts to pointer types but doesn't convey much 
>information to the user.

Initially, when I was converting to C++ from C, I wanted to use NULL,NIL, ZERO 
or any symbolic name. Once I read D & E I got very comfortable with the humble 
0. It coveys more than enough information for me.
        
>       - the type of 0 is "const int". Overloading a function to take a null va
>lue 
>based on const int also allows any integer value to be passed in, and the 
>error cannot be detected at compile-time.

Personally, I don't see much ( if any ) need to be able to overload 
specifically on a null pointer over any other pointer.

/ikh
     
     

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