default random object?

[Andrei Alexandrescu]

bearophile wrote:
> Andrei Alexandrescu:
> 
>> 3. How should the global rng be initialized?
> 
> Automatically seeded with the time at the beginning of the program. Of course the seed can be set again in any moment.
> 
> 
>> 4. While we're at it, should uniform(a, b) generate by default something 
>> in [a, b] or [a, b)? Someone once explained to me that generating [a, b] 
>> for floating point numbers is the source of all evils and that Hitler, 
>> Stalin and Kim Il Sung (should he still be alive) must be using that 
>> kind of generator. Conversely, generating [a, b) is guaranteed to bring 
>> in the long term everlasting peace to Earth. My problem however is that 
>> in the integer realm I always want to generate [a, b]. Furthermore, I 
>> wouldn't be happy if the shape of the interval was different for 
>> integers and floating point numbers. How to break this conundrum? Don't 
>> forget that we're only worrying about defaults, explicit generation is 
>> always possible with self-explanatory code:
>> auto rng = Random(unpredictableSeed);
>> auto a = 0.0, b = 1.0;
>> auto x1 = uniform!("[]")(rng, a, b);
>> auto x2 = uniform!("[)")(rng, a, b);
>> auto x3 = uniform!("(]")(rng, a, b);
>> auto x4 = uniform!("()")(rng, a, b);
> 
> That's awful and ugly. My suggestions are simple (copied from my dlibs and the random std lib of Python):
> 
> random() => floating point [0, 1)
> randInt(a=0, b) => integral [a, b]
> randRange(a=0, b) => integral [a, b)
> uniform(a, b) => floating point [a, b)
> normal(a, b) => good quality normally-distributed number with given std dev and avg.

Leaving normal() aside (does your implementation implement the ziggurat 
algorithm? If so, would you agree to contribute it to phobos?), I don't 
see how having to memorize four names instead of one is necessarily 
awesome and beautiful. Besides uniform() renders "random" redundant. 
Hardly a pinnacle of good API design, see realloc() which essentially 
makes malloc() and free() redundant.

Andrei