What does << mean in Ruby?

Question

I have code:

  def make_all_thumbs(source)
    sizes = [\'1000\',\'1100\',\'1200\',\'800\',\'600\']
    threads = []
    sizes.each do |s|
      threads <         


        

Answer 1

Also, since Ruby 2.6, the << method is defined also on Proc.

Proc#<< allows to compose two or more procs.

Answer 2

Mostly used in arrays to append the value to the end of the array.

a = ["orange"]
a << "apple"
puts a

gives this

  ["orange", "apple"] 

result.