Find all indices of a substring within a string

Question

I want to be able to find the index of all occurrences of a substring in a larger string using Ruby. E.g.: all "in" in "Einstein"

str = "Einstein"
str.index("in") #returns only 1
str.scan("in")  #returns ["in","in"]
#desired output would be [1, 6]

Answer 1

The standard hack is:

indices = "Einstein".enum_for(:scan, /(?=in)/).map do
  Regexp.last_match.offset(0).first
end
#=> [1, 6]