Ruby: Is there something like Enumerable#drop that returns an enumerator instead of an array?

Question

I have some big fixed-width files and I need to drop the header line.

Keeping track of an iterator doesn't seem very idiomatic.

# This is what I do now.
File.open(filename).each_line.with_index do |line, idx|
  if idx > 0
     ...
  end
end

# This is what I want to do but I don't need drop(1) to slurp
# the file into an array.
File.open(filename).drop(1).each_line do { |line| ... }

What's the Ruby idiom for this?

Answer 1

This is slightly neater:

File.open(fname).each_line.with_index do |line, lineno|
  next if lineno == 0
  # ...
end

or

io = File.open(fname)
# discard the first line
io.gets
# process the rest of the file
io.each_line {|line| ...}
io.close

Answer 2

If you need it more than once, you could write an extension to Enumerator.

class Enumerator
  def enum_drop(n)
    with_index do |val, idx|
      next if n == idx
      yield val
    end
  end
end

File.open(testfile).each_line.enum_drop(1) do |line|
  print line
end

# prints lines #1, #3, #4, …