Program logic bugs vs input/environmental errors

[eles via Digitalmars-d]

On Wednesday, 8 October 2014 at 07:00:38 UTC, Dominikus Dittes 
Scherkl wrote:
> On Wednesday, 8 October 2014 at 01:22:49 UTC, Timon Gehr wrote:

> If he would ever open the right door, you would just take it 
> too.

Almost. If he opens the winning door, he gives you another very 
important information: the correctness of your first choice. If 
you already know if your first choice is correct or wrong, then 
having the host opening a door (does not matter which of the 
remaining two, in this case) solves the problem without ambiguity.

But, when you make your second choice, you still not know if your 
first choice was correct or not. The only thing that you know is 
that the chance that your first choice was correct is two times 
less than the chance it was wrong.

So you bet that your first choice was wrong, and you move on to 
the next problem, which, assuming this bet, now becomes a 
non-ambiguous problem.

The key is this: "how would a third person bet on my first 
choice?" Reasonably, he would bet that the choice is wrong. So 
why wouldn't I do the same?