random number including 1 - i.e. [0,1]

[Robert Kern]

On 2009-06-10 14:46, Mark Dickinson wrote:
> On Jun 10, 8:15 pm, Robert Kern<robert.k... at gmail.com>  wrote:
>> On 2009-06-10 13:53, Terry Reedy wrote:
>>> A full technical discussion does not below in the docs, in my opinion. A
>>> wike article would be fine.
>> True. However, a brief note that "Due to floating point arithmetic, for some
>> values of a and b, b may or may not be one of the possible generated results."
>> might be worthwhile. The actual details of *why* this is the case can be
>> discussed elsewhere.
>
> I find it difficult to see how such a disclaimer would have any
> practical
> value, without also knowing *which* values of a and b are affected.
>
> It can certainly be useful to know that endpoints *aren't* included
> where
> that's true.  For example, knowing that random.random() can never
> produce the
> value 1.0 means that one can safely generate a mean 1 exponential
> variate with
> -log(1-random.random()), without worrying about the possibility of
> taking log
> of 0.
>
> But I don't know why it would be useful to know that endpoints *are*
> sometimes
> included, without knowing exactly when.

That's a fair point. However, one issue that hasn't been brought up is that it 
might be confusing to a user why random.random() returns values in a half-open 
interval while random.uniform() claims a closed interval. Even for reasonably 
sophisticated floating point users, it's not necessarily obvious that that is 
the reasoning behind the different claims.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco