Iterates over a numeric range.

(rn x) is equivalent to (rn 0 x).

(rn x y z) iterates from x inclusive to y exclusive, incrementing by z each time.

(rn x #n z) endlessly counts upwards or downwards from x, incrementing the counter by z each time.

If any argument is a float, then the iterator will produce floats. Otherwise, it will produce integers.

If z is less than 0, iteration is finished when the counter is <= y. Otherwise, iteration ends when the counter is >= y.

(prn (arr ..(rn 3))) ; prints (0 1 2)
(prn (arr ..(rn 0 3))) ; prints (0 1 2)
(prn (arr ..(rn 0 3 1.0))) ; prints (0.0 1.0 2.0)

(prn (arr ..(rn 2 14 3))) ; prints (2 5 8 11)
(prn (arr ..(rn 2 14 -1))) ; prints ()
(prn (arr ..(rn 2 2 -1))) ; prints ()
(prn (arr ..(rn 5 0 -1))) ; prints (5 4 3 2 1)