switch_around

nemostultae (Daniel) — Wed, 21 Dec 2005 22:16:39 GMT



require 'enumerator'



# Returns an object of the argument's class with each_slice of 2 switched around.

# Works on any object that mixes in #each

# 

# Examples:

# switch_around("foo!")       #=> of!o

# switch_around((1..10).to_a) #=> [2, 1, 4, 3, 6, 5, 8, 7, 10, 9]

def switch_around(data)

  switched_data = data.class.new

  

  # When appending to a string ints will have #chr called on them, so protect against 

  # error about sending a message to nil. b will only be nil when the  collection is 

  # an odd length. Of course, this creates a bug. For example we could have an Array with 

  # embedded nils, so we must also check if it is a String (again...)

  switch_proc = lambda do |a,b|

    switched_data << b unless b.nil? and data.is_a?(String)

    switched_data << a

  end

  

  # String#each enumerates over lines, so we must change it to enumerate over bytes.

  if data.is_a?(String)

    data.to_enum(:each_byte).each_slice(2) { |a,b| switch_proc.call(a, b) }

  else

    data.each_slice(2) { |a,b| switch_proc.call(a,b) }

  end

  

  switched_data

end

each_slice

nemostultae (Daniel) — Fri, 30 Sep 2005 16:50:45 GMT



require 'enumerator'



(1..10).each_slice(2) { |n| p n }

# [1, 2]

# [3, 4]

# [5, 6]

# [7, 8]

# [9, 10]

DZone Snippets: Nemostultae's Code Snippets

switch_around

each_slice