Declaring an integer Range with step != 1 in Ruby - ruby

Question

UPDATE 2: For posterity, this is how I've settled on doing it (thanks to Jorg's input):
100.step(2, -2) do |x|
# my code
end
(Obviously there are plenty of ways to do this; but it sounds like this is the most "Ruby" way to do it; and that's exactly what I was after.)
UPDATE: OK, so what I was looking for was step:
(2..100).step(2) do |x|
# my code
end
But it turns out that I wasn't 100% forthcoming in my original question. I actually want to iterate over this range backwards. To my surprise, a negative step isn't legal.
(100..2).step(-2) do |x|
# ArgumentError: step can't be negative
end
So: how do I do this backwards?
I am completely new to Ruby, so be gentle.
Say I want to iterate over the range of even numbers from 2 to 100; how would I do that?
Obviously I could do:
(2..100).each do |x|
if x % 2 == 0
# my code
end
end
But, obviously (again), that would be pretty stupid.
I know I could do something like:
i = 2
while i <= 100
# my code
i += 2
end
I believe I could also write my own custom class that provides its own each method (?). I am almost sure that would be overkill, though.
I'm interested in two things:
Is it possible to do this with some variation of the standard Range syntax (i.e., (x..y).each)?
Either way, what would be the most idiomatic "Ruby way" of accomplishing this (using a Range or otherwise)? Like I said, I'm new to the language; so any guidance you can offer on how to do things in a more typical Ruby style would be much appreciated.

Answer 1

You can't declare a Range with a "step". Ranges don't have steps, they simply have a beginning and an end.
You can certainly iterate over a Range in steps, for example like this:
(2..100).step(2).reverse_each(&method(:p))
But if all you want is to iterate, then what do you need the Range for in the first place? Why not just iterate?
100.step(2, -2, &method(:p))
This has the added benefit that unlike reverse_each it does not need to generate an intermediate array.

Answer 2

This question answers yours: about ruby range?
(2..100).step(2) do |x|
# your code
end

Answer 3

I had similar issue here are the various ways I found to do the same SIMPLE thing I used step in the end because it allowed for NEGATIVE and FRACTIONAL increments and I had no conditions, other than the bounds to look for
case loop_type
when FOR
# doen't appear to have a negative or larger than 1 step size!
for kg in 50..120 do
kg_to_stones_lbs(kg)
end
when STEP
120.step(70,-0.5){ |kg|
kg_to_stones_lbs(kg)
}
when UPTO
50.upto(120) { |kg|
kg_to_stones_lbs(kg)
}
when DOWNTO
120.downto(50){ |kg|
kg_to_stones_lbs(kg)
}
when RANGE
(50..120).reverse_each{ |kg|
kg_to_stones_lbs(kg)
}
when WHILE
kg = 120
while kg >= 50
kg_to_stones_lbs(kg)
kg -= 0.5
end
end
O/P:
92.0kg - 14st 7lbs
91.5kg - 14st 6lbs
91.0kg - 14st 5lbs
90.5kg - 14st 4lbs
90.0kg - 14st 2lbs
89.5kg - 14st 1lbs
89.0kg - 14st 0lbs
88.5kg - 13st 13lbs
88.0kg - 13st 12lbs