Is there something like Julia `rsplit` for Crystal?

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1

Is there something like Julia rsplit for Crystal ?

2

String#rpartition would be equivalent to rsplit(limit = 2).
Without limit, you could call #reverse on the result of String#split.

3 
def rsplit(s : String, sep : Char | String, limit : Int32 = 0, remove_empty : Bool = true, & : String ->)
  limit = Int32::MAX if limit <= 0
  count = 1
  offset = s.size - 1
  sep_size = sep.is_a?(Char) ? 1 : sep.size

  while offset >= 0
    off = offset - sep_size + 1
    if count < limit && off >= 0 && (index = s.rindex(sep, offset: off))
      unless remove_empty && index == off
        count += 1
        return if (yield s[(index + sep_size)..offset]) == Iterator.stop
      end
      offset = index - 1
    else
      yield s[..offset]
      return
    end
  end
end

Maybe it would be better to iterate the characters directly instead of “rindex”

4

A dedicated implementation like rindex should technically be more optimized. However, it is not as good as it could be because it returns a character index, so slicing from that is very inefficient. We’re missing an implementation of byte_rindex to make this really efficient.
Iterating characters would also get ugly it the separator is a string.