Two dots in an equation

Question

So recently, I've been looking into attractors. However when I stumbled upon the Lu Chen attractor, one of the example values for a variable was "-15..15" I was thoroughly confused as I have never seen a number with two decimal dots. I first thought it might have been a typo and was supposed to be -15.15 but when I plotted that number in instead of whatever -15..15 is supposed to be, I got entirely different results. Can someone please help me?

Website: https://en.wikipedia.org/wiki/Multiscroll_attractor#Lu_Chen_attractor

Under the parameters, for the variable u, it says "u = -15..15" What does that mean?

Answer 1

The numbers $-15$ through $15$, an interval. Usually an integer interval.

Answer 2

They mean, $u\in\{-15,..,15\}$, or sometimes $u\in[-15;15]$ if floating values are permissable.   Most usually, iterations are over integers.

Answer 3

As other people has also commented, he would probably mean the set $[-15, 15]$. This means $\{-15, -14, \dots, 15\}$.

I just want to add that this notation is quite frequent in Computer Science papers (and not so common in maths ones). For instance, one may write this note about Quicksort algorithm:

When we apply partition function to an arbitrary vector $v = \langle v_0, v_1, \dots, v_{n-1} \rangle$ with $n$ elements, we split $v$ in three parts: a subvector $s_1 = v[0..k-1]$, a pivot $v[k]$ and the rest of the vector, $s_2 = v[k+1..n-1]$ (with $0\leq k \leq n)$...

Note that here, by $v[a..b]$ we are representing the ordered sequence of elements $\langle v_a, v_{a+1}, \dots, v_b\rangle$ (supposing $a \leq b$), which is a complete different meaning from math papers.