v		input view
count		number of rows in result
start		index of first row
rate		repetition factor for each input row
ssize		step size from one row to the next

Step is a general version of {slice} which also supports repetition of rows before moving on to the next step. This operator is used to implement {slice}, {repeat}, and {spread}.

set v [view A def {a b c}]

view $v step 3 0 4 2

	A
0	a
1	a
2	a
3	a
4	c
5	c
6	c
7	c
8	b
9	b
10	b
11	b