How can I iterate over a reversed range with a specific step in Ruby?

Question

I can iterate like this

(0..10).step(2){|v| puts v}

but, since reversed range is equal to empty range, I cannot iterate this way

(10..0).step(2){|v| puts v}

it will earn me nothing. Of course, I can iterate backward like this

10.downto(0){|v| puts v}

but downto method doesn't allow me to set other step except default 1. It's something very basic, so I suppose there should be a built-in way to do this, which i don't know.

Answer 1

Why don't you use Numeric#step:

From the docs:

Invokes block with the sequence of numbers starting at num, incremented by step (default 1) on each call. The loop finishes when the value to be passed to the block is greater than limit (if step is positive) or less than limit (if step is negative). If all the arguments are integers, the loop operates using an integer counter. If any of the arguments are floating point numbers, all are converted to floats, and the loop is executed floor(n + n*epsilon)+ 1 times, where n = (limit - num)/step. Otherwise, the loop starts at num, uses either the < or > operator to compare the counter against limit, and increments itself using the + operator.

irb(main):001:0> 10.step(0, -2) { |i| puts i }
10
8
6
4
2
0