About DbC, pros & cons

[Walter Bright]

retard wrote:
> 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?

I didn't make any comment about that.

> 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) ?

I didn't say they did.

I'm wondering what you read that led you to these questions?