Question

Looking at @mu is too short’s answer to another question, I tried a variation:

def anagrams(list)
  h = Hash.new{ [] }
  list.each_with_object(h){ |el, h| h[el.downcase.chars.sort] <<= el }
end

anagrams(['cars', 'for', 'potatoes', 'racs', 'four','scar', 'creams', 'scream'])

(Blindly assuming there would be a<<= operator.) It works, but Hash.new{[]} is not idiomatic at all – I have not found any examples. Is there something wrong with it?

Answer 1

It’s weird, because it doesn’t make any use of what the block ctor provides, but the purpose of the block ctor is to return the default value–if you choose not to do anything with the |h, k|, that’s your call.