Divisibility testing

We can test whether one number evenly divides another using the divides operator. In particular, a divides b is true if there exists an integer k such that b == k*a. For example:

Disco> 3 divides 6
true
Disco> 6 divides 3
false
Disco> 3 divides (-6)
true
Disco> 5 divides 5
true
Disco> 4 divides 6
false
Disco> 0 divides 10
false
Disco> 10 divides 0
true
Disco> 0 divides 0
true
Disco> 1/2 divides 3/2
true