koobas.hobune.stream
Random.Range changed in Unity 5?
In online documentation it states currently that Random.Range(float a, float b) will return value in range [a, b), but in earlier versions of documentation it was [a, b], so i wonder if they've changed function behavior(which is crazy it would lead to impossible to debug miracle bugs) or it is a simple documentation mistake?
watch out for the difference in int versus float versions??
Even if it is a change, I can't see it breaking any real code. And it looks like just a doc fix.
In theory [1.0,2.0] could generate 2.0 exactly, but no one would ever count on actually rolling a 2.00000. The odds are 1 out of 2^23(?). And losing that number changes the probability space by an infinitesimal amount.
And everyone "knows" all random funcs never rolls the top number. I suspect most people, myself included, just assumed the range was really the standard [) or maybe even (). The normal way to write code with random float ranges is to assume it will never be an end value, but allow that it could be.
So if it infinitesimal (with this i'm not quite agree) why change it at all? [) is by no means standart (c++ rand() is [0, RAND_$$anonymous$$AX] for example)
But what Owen says about how to code using random floats applies just as much in C++ as in Unity. The point is that getting a random float and then testing its equality to any specific value (not just the bounds) is a weird thing to do.
I can verify that it seems they just messed up the documentation (once again^^). Here's a test that proofs that the max value is inclusive:
IEnumerator Start()
{
float max = 2.0f;
while (!Input.GetKeyDown(KeyCode.Return))
{
for (int i = 0; i < 100000; i++)
{
float v = Random.Range(0f, max);
if (v == max)
Debug.Log("Match " + v.ToString("0.000000000"));
}
yield return null;
}
}
At about 75 fps (7.5 million values per sec.) I get a "Match" on average every 2 - 4 seconds.
So nothing has changed, just the docs. Feel free to file a bug report in Unity. There's a category for documentation.
edit
btw. "RAND_MAX" in C++ isn't a variable you set. It's just a constant and it represents by definition "the maximum value returned by rand". Most random generators produce values within the32 or 64 bit unsigned integer range. The way you apply a max value is by using the modulo on the returned number. The modulo automatically excludes this value:
0 % 3 == 0
1 % 3 == 1
2 % 3 == 2
3 % 3 == 0
4 % 3 == 1
5 % 3 == 2
6 % 3 == 0
It's the same logic as with zero based indices. Since zero is a value as well the value you specify as max devines the count of possible values.
for mix max you usually use:
min + rand() % (max-min)
But the docs say "Returns a random float number between and $$anonymous$$ [inclusive] and max [inclusive] (Read Only)." Which is what the Unity 4 docs say.
Yes, it used to be both inclusive for the float version. However they have changed it in the docs.
The docs are changed way to often and the funny thing is they always change things which don't need to be changed and those things which are wrong for ages stay ^^.
