About DbC, pros & cons

[retard]

Sat, 02 Oct 2010 10:25:25 -0700, Walter Bright wrote:

> retard wrote:
>> A modern developer would actually use Python to write code for the
>> space shuttle. Walter had this article about hardware/software
>> reliability. If you write 20 implementations of the same program in
>> Python and let the computers vote, you'll get much safer systems than
>> with statically typed languages.
> 
> That's a misunderstanding of what I wrote. I wrote that to get safer
> systems, the redundant systems must be independent of each other - the
> more independent, the better. For example:
> 
> 1. different CPUs
> 2. different hardware
> 3. different programming languages
> 4. different algorithms
> 5. different programming teams
> 
> Static or dynamic typing has nothing to do with it, unless you use one
> in one system and the other in the other.
> 
> 20 implementations in Python may all fail to the same problem with the
> Python runtime.

And how is static type system any better in this regard? Multiple 
implementations satisfies points 5), 4), and partially or fully 3) above 
(assuming we use several different dynamic languages). How can static 
type systems guarantee 1) and 2) ?