boolean true and false values.

[Tim Rowe]

In article <slrn8lgsjq.us.hat at se-46.wpa.wtb.tue.nl>, 
hat at se-46.wpa.wtb.tue.nl (Albert Hofkamp) wrote:

The other comments have been addressed, but:

> >But that's /exactly/ right! If you execute 'total="kjerg"' then your 
> >invariant is indeed violated!
> 
> So, why is it then that Python allows this ?
> For a language aimed at professionals, I understand (although I wouldn't
> introduce it), but for a clean language such as Python ?

If you execute 'total = total - rand()' your invariant will probably be 
broken too, in a typed language or an untyped language. No language will 
stop you writing code that violates invariants! Some help you find out 
that you've done it, though; Python's (and C's and C++'s) assert() helps. 
Eiffel's contracts help even more. But this is not a typing issue.