module Enumerable
#
# 'true' if the Enumerable has no elements
#
def blank?
not any?
end
#
# `.all` is more fun to type than `.to_a`
#
alias_method :all, :to_a
#
# `includes?` is gramatically correct.
#
alias_method :includes?, :include?
#
# Skip the first n elements and return an Enumerator for the rest, or pass them
# in succession to the block, if given. This is like "drop", but returns an enumerator
# instead of converting the whole thing to an array.
#
def skip(n)
if block_given?
each do |x|
if n > 0
n -= 1
else
yield x
end
end
else
enum_for :skip, n
end
end
#
# Split this enumerable into chunks, given some boundary condition. (Returns an array of arrays.)
#
# Options:
# :include_boundary => true #=> include the element that you're splitting at in the results
# (default: false)
# :after => true #=> split after the matched element (only has an effect when used with :include_boundary)
# (default: false)
# :once => flase #=> only perform one split (default: false)
#
# Examples:
# [1,2,3,4,5].split{ |e| e == 3 }
# #=> [ [1,2], [4,5] ]
#
# [1,2,3,4,5].split(:include_boundary=>true) { |e| e == 3 }
# #=> [ [1,2], [3,4,5] ]
#
# chapters = File.read("ebook.txt").split(/Chapter \d+/, :include_boundary=>true)
# #=> [ ["Chapter 1", ...], ["Chapter 2", ...], etc. ]
#
def split_at(matcher=nil, options={}, &block)
# TODO: Ruby 1.9 returns Enumerators for everything now. Maybe use that?
return self unless self.any?
include_boundary = options[:include_boundary] || false
if matcher.nil?
boundary_test_proc = block
else
if matcher.is_a? String or matcher.is_a? Regexp
boundary_test_proc = proc { |element| element[matcher] rescue nil }
else
boundary_test_proc = proc { |element| element == matcher }
#raise "I don't know how to split with #{matcher}"
end
end
chunks = []
current_chunk = []
splits = 0
max_splits = options[:once] == true ? 1 : options[:max_splits]
each do |e|
if boundary_test_proc.call(e) and (max_splits == nil or splits < max_splits)
if current_chunk.empty? and not include_boundary
next # hit 2 boundaries in a row... just keep moving, people!
end
if options[:after]
# split after boundary
current_chunk << e if include_boundary # include the boundary, if necessary
chunks << current_chunk # shift everything after the boundary into the resultset
current_chunk = [] # start a new result
else
# split before boundary
chunks << current_chunk # shift before the boundary into the resultset
current_chunk = [] # start a new result
current_chunk << e if include_boundary # include the boundary, if necessary
end
splits += 1
else
current_chunk << e
end
end
chunks << current_chunk if current_chunk.any?
chunks # resultset
end
#
# Split the array into chunks, cutting between the matched element and the next element.
#
# Example:
# [1,2,3,4].split_after{|e| e == 3 } #=> [ [1,2,3], [4] ]
#
def split_after(matcher=nil, options={}, &block)
options[:after] ||= true
options[:include_boundary] ||= true
split_at(matcher, options, &block)
end
#
# Split the array into chunks, cutting between the matched element and the previous element.
#
# Example:
# [1,2,3,4].split_before{|e| e == 3 } #=> [ [1,2], [3,4] ]
#
def split_before(matcher=nil, options={}, &block)
options[:include_boundary] ||= true
split_at(matcher, options, &block)
end
#
# Sum the elements
#
def sum
if block_given?
inject(0) { |total,elem| total + yield(elem) }
else
inject(0) { |total,elem| total + elem }
end
end
#
# Average the elements
#
def average
count = 0
sum = inject(0) { |total,n| count += 1; total + n }
sum / count.to_f
end
#
# The same as "map", except that if an element is an Array or Enumerable, map is called
# recursively on that element.
#
# Example:
# [ [1,2], [3,4] ].deep_map{|e| e ** 2 } #=> [ [1,4], [9,16] ]
#
def deep_map(depth=nil, &block)
map do |obj|
case obj
when Enumerable
obj.deep_map(&block)
else
block.call(obj)
end
end
end
alias_method :recursive_map, :deep_map
alias_method :map_recursively, :deep_map
alias_method :map_recursive, :deep_map
#
# The same as "select", except that if an element is an Array or Enumerable, select is called
# recursively on that element.
#
# Example:
# [ [1,2], [3,4] ].deep_select{|e| e % 2 == 0 } #=> [ [2], [4] ]
#
def deep_select(depth=nil, &block)
map do |*args|
if depth.nil? or depth > 0
case obj
when Hash
when Array, Enumerable
result = obj.deep_select(depth ? depth-1 : nil, &block)
result.any? ? result : nil
end
else
obj if block.call(obj)
end
end.compact
end
alias_method :recursive_select, :deep_select
#
# Identical to "reduce" in ruby1.9 (or foldl in haskell.)
#
# Example:
# array.foldl{|a,b| a + b } == array[1..-1].inject(array[0]){|a,b| a + b }
#
def foldl(methodname=nil, &block)
result = nil
raise "Error: pass a parameter OR a block, not both!" unless !!methodname ^ block_given?
if methodname
each_with_index do |e,i|
if i == 0
result = e
next
end
result = result.send(methodname, e)
end
else
each_with_index do |e,i|
if i == 0
result = e
next
end
result = block.call(result, e)
end
end
result
end
#
# Returns the powerset of the Enumerable
#
# Example:
# [1,2].powerset #=> [[], [1], [2], [1, 2]]
#
def powerset
# the bit pattern of the numbers from 0..2^(elements)-1 can be used to select the elements of the set...
a = to_a
(0...2**a.size).map do |bitmask|
a.select.with_index{ |e, i| bitmask[i] == 1 }
end
end
#
# Does the opposite of #zip -- converts [ [:a, 1], [:b, 2] ] to [ [:a, :b], [1, 2] ]
#
def unzip
# TODO: make it work for arrays containing uneven-length contents
to_a.transpose
end
#
# Associative grouping; groups all elements who share something in common with each other.
# You supply a block which takes two elements, and have it return true if they are "neighbours"
# (eg: belong in the same group).
#
# Example:
# [1,2,5,6].group_neighbours_by { |a,b| b-a <= 1 } #=> [ [1,2], [5,6] ]
#
# (Note: This is a very fast one-pass algorithm -- therefore, the groups must be pre-sorted.)
#
def group_neighbours_by(&block)
result = []
cluster = [first]
each_cons(2) do |a,b|
if yield(a,b)
cluster << b
else
result << cluster
cluster = [b]
end
end
result << cluster if cluster.any?
result
end
alias_method :group_neighbors_by, :group_neighbours_by
#
# Convert the array into a stable iterator (Iter) object.
#
def to_iter
Iter.new(to_a)
end
alias_method :iter, :to_iter
end