Swapping variable values using multiple assignment in Lua
Lua allows multiple assignment, where a list of values is assigned to a list of variables in one step. Both lists have their elements separated by commas. For instance, in the assignment
a, b = 10, 2*x
the variable a gets the value 10 and b gets 2*x.
In a multiple assignment, Lua first evaluates all values and only then executes the assignments. Therefore, we can use a multiple assignment to swap two values, as in
x, y = y, x -- swap `x' for `y'
a[i], a[j] = a[j], a[i] -- swap `a[i]' for `a[j]'
[Source: lua.org: 4.1 Assignment]
