How to populate and array in Ruby using upto or '..'

Question

I initialize my array

my_array = Array.new(26)

and then try to populate it

my_array[0..25] = ["A".."Z"]
# => "A".."Z"

Same output when I try:

my_array[0..25] = "A".upto("Z")
# => "A".."Z"

When I try using a block:

my_array[0..25] = "A".upto("Z") { |l| l} #=> "A"
my_array
# => ["A"]

When after trying the first or second method of populating above, I inspect my_array:

my_array
# => ["A".."F"]

which I understand is an enumerator. So I try:

my_array.each {|l| p l}

but all I'm returned is

"A..F"
# => ["A".."F"]

What is actually being stored in the array?

How can I correctly implement the populating of the array with the letters of the alphabet?

Eli Sadoff · Accepted Answer · 2016-10-18 16:07:59Z

1

Ruby actually has a method called to_a and you can convert a range to an array. So if I wanted a variable with all the letters of the alphabet using a range I could do alphabet = ('a'..'z').to_a. Also, ruby is dynamically typed and you do not need to initialize an array. a = [1,2,3] is all you need to do. You would not need to do

a = Array.new(3)
a = [1,2,3]

answered Oct 18, 2016 at 16:07

Eli Sadoff

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1 Comment

PakiPat Over a year ago

So I basically needed to change the enumerator ('A..Z') to an array type. Dang! Wish I'd asked earlier. :) Thanks.

Cary Swoveland · Accepted Answer · 2016-10-18 18:18:24Z

my_array = Array.new(26)

my_array[0..25] = ["A".."Z"]
#=> "A".."Z"

my_array.size
  #=> 1
my_array.first
  #=> "A".."Z"
my_array.first.is_a? Range
  #=> true

Had we initially written my_array = [] the results would have been the same.

The easiest way to obtain what you want is to splat the range:

my_array = []
my_array[0..25] = *"A".."Z"
  #=> ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
  #    "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]

which is equivalent to

my_array[0..25] = "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
                  "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

but this can be done in a single operation:

my_array = *"A".."Z"
  #=> ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
  #    "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]

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