dynamic classes and duck typing

[Don]

BCS wrote:
> Hello dsimcha,
> 
>> == Quote from BCS (none at anon.com)'s article
>>
>>> I don't have a link or anything but I remember hearing about a study
>>> MS did
>>> about finding bugs and what they found is that every reasonably
>>> effective
>>> tool they looked at found the same amount of bugs (ok, within
>>> shouting distance,
>>> close enough that none of them could be said to be pointless) but
>>> different
>>> bugs. The way to find the most bugs is to attack it from many angle.
>>> If I
>>> can have a language that can totally prevent one class of bugs in
>>> vast swaths
>>> of code, that's a good thing, even if it does jack for another class
>>> of bugs.
>>
>> Right, but the point I was making is that you hit diminishing returns
>> on static verification very quickly.  If you have even very basic
>> static verification, it will be enough to tilt the vast majority of
>> your bugs towards high-level logic/algorithm bugs.
>>
> 
> OTOH, if it's done well (doesn't get in my way) and's built into the 
> language, any static verification is free from the end users standpoint. 
> Heck, even it it gets in your way but only for strange cases where your 
> hacking around, it's still useful because it tells you where the high 
> risk code is.

There's a really interesting synergy between pure and unit tests. It's 
much easier to test a function properly if it's pure -- you know that 
there are no globals anywhere which you have to worry about.