null references redux + Looney Tunes

[Andrei Alexandrescu]

Nick Sabalausky wrote:
> "Justin Johansson" <no at spam.com> wrote in message 
> news:haavf1$2gs7$1 at digitalmars.com...
>> It's a difficult challenge to get high performance, readable and 
>> maintainable code out of complex number
>> intensive algorithms.   Use of library types for complex numbers has, in 
>> my experience been problematic.
>> Complex numbers should be first class value types I say.
>>
> 
> There's been discussion before (I can't find it now, or remember the name 
> for it) of type systems that allow for proper handling of things like m/s 
> vs. m/(s*s) vs inch/min etc. I haven't actually worked with such a feature 
> or with complex/imaginary numbers in any actual code, so I can't be sure, 
> but I've been wondering if a type system like that would be an appropriate 
> (or even ideal) way to handle real/complex/imaginary numbers.

It better be. Complex numbers aren't that complicated of a notion. 
What's lost in pulling them out of the language is the ability to define 
literals. Now please name five remarkable complex literals.

The feature you're referring to is called dimensional analysis.

> (I've also 
> been wondering if it might be a huge benefit for distinguishing between 
> strings that represent a filename vs file content vs file-extention-only vs 
> relative-path+filename, vs absolute-path-only, etc. I've been really wanting 
> a better way to handle that than just a variable naming convention.) 

I don't quite think so. In fact I don't think so at all. Pathnames of 
various flavors evolve quite a bit in many programs, and having to worry 
about tracking their type throughout is too much aggravation to be 
worthwhile. Last thing I'd want when manipulating pathnames would be a 
sticker of a library slapping my wrist anytime I misuse one of its six 
dedicated types.


Andrei