Null references redux

[Andrei Alexandrescu]

Walter Bright wrote:
> Denis Koroskin wrote:
>  > On Sat, 26 Sep 2009 22:30:58 +0400, Walter Bright
>  > <newshound1 at digitalmars.com> wrote:
>  >> D has borrowed ideas from many different languages. The trick is to
>  >> take the good stuff and avoid their mistakes <g>.
>  >
>  > How about this one:
>  > 
> http://sadekdrobi.com/2008/12/22/null-references-the-billion-dollar-mistake/ 
> 
>  >
>  >
>  > :)
> 
> I think he's wrong.
> 
> Getting rid of null references is like solving the problem of dead 
> canaries in the coal mines by replacing them with stuffed toys.
> 
> It all depends on what you prefer a program to do when it encounters a 
> program bug:
> 
> 1. Immediately stop and produce an indication that the program failed
> 
> 2. Soldier on and silently produce garbage output
> 
> I prefer (1).
> 
> Consider the humble int. There is no invalid value such that referencing 
> the invalid value will cause a seg fault. One case is an uninitialized 
> int is set to garbage, and erratic results follow. Another is that (in 
> D) ints are default initialized to 0. 0 may or may not be what the logic 
> of the program requires, and if it isn't, again, silently bad results 
> follow.
> 
> Consider also the NaN value that floats are default initialized to. This 
> has the nice characteristic of you know your results are bad if they are 
> NaN. But it has the bad characteristic that you don't know where the NaN 
> came from. Don corrected this by submitting a patch that enables the 
> program to throw an exception upon trying to use a NaN. Then, you know 
> exactly where your program went wrong.
> 
> It is exactly analogous to a null pointer exception. And it's darned 
> useful.

My assessment: the chances of convincing Walter he's wrong are quite 
slim... Having a rationale for being wrong is very hard to overcome.

Andrei