Non-null objects, the Null Object pattern, and T.init

[Walter Bright]

On 1/17/2014 2:05 PM, H. S. Teoh wrote:
> Of course, but that requires a few rounds of recompilation, repacking
> the EEPROM image, installation on device, and repeating a user
> interaction that possibly only randomly hits the bug. Hardly the work of
> a few minutes.

I've done EEPROM programming & debugging, I know how to do it. Nulls still 
aren't a special kind of bug.

BTW, even back in the 1970's, people developing EEPROM systems would plug a 
special device into the board which would redirect the EEPROM access to some 
off-board RAM, or would debug using emulators. Maybe this technology has been 
forgotten :-)


> But in many cases, the source of a bad value is easy to find because of
> its uniqueness (hmm, why does variable x have a value of 24576? oh I
> know, search for 24576 in the code). Nulls, though, can occur in many
> places, and in D they are implicit. There's no easy way to search for
> that.

Come on. Every type in D has a default initializer. There's still nothing 
special about null.

Even if you got rid of all the nulls and instead use the null object pattern, 
you're not going to find it any easier to track it down, and you're in even 
worse shape because now it can fail and you may not even detect the failure, or 
may discover the error much, much further from the source of the bug.