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|
unless Enumerable.method_defined? :lazy
require 'backports/tools/arguments'
require 'backports/1.9.1/enumerator/new'
module Enumerable
def lazy
klass = Enumerator::Lazy.send :class_variable_get, :@@lazy_with_no_block # Note: class_variable_get is private in 1.8
Enumerator::Lazy.new(klass.new(self, :each, []))
end
end
class Enumerator
class Yielder
# Current API for Lazy Enumerator does not provide an easy way
# to handle internal state. We "cheat" and use yielder to hold it for us.
# A new yielder is created when generating or after a `rewind`.
# This way we avoid issues like http://bugs.ruby-lang.org/issues/7691
# or http://bugs.ruby-lang.org/issues/7696
attr_accessor :backports_memo
end
class Lazy < Enumerator
@@done = :__backports_lazy_enumeration_done__ # used internally to bail out of an iteration
@@lazy_with_no_block = Struct.new(:object, :method, :args) # used internally to create lazy without block
def initialize(obj)
if obj.is_a?(@@lazy_with_no_block)
@inspect_info = obj
return super(@receiver = obj.object, @method = obj.method || :each, * @args = obj.args)
end
raise ArgumentError, "must supply a block" unless block_given?
@receiver = obj
super() do |yielder, *args|
catch @@done do
obj.each(*args) do |*x|
yield yielder, *x
end
end
end
end
alias_method :force, :to_a
def lazy
self
end
def to_enum(method = :each, *args)
Lazy.new(@@lazy_with_no_block.new(self, method, args))
end
alias_method :enum_for, :to_enum
def inspect
suff = ''
suff << ":#{@method}" unless @method.nil? || @method == :each
suff << "(#{@args.inspect[1...-1]})" if @args && !@args.empty?
"#<#{self.class}: #{@receiver.inspect}#{suff}>"
end
{
:slice_before => //,
:with_index => [],
:cycle => [],
:each_with_object => 42,
:each_slice => 42,
:each_entry => [],
:each_cons => 42,
}.each do |method, args|
next unless Enumerator.method_defined? method
unless [].lazy.send(method, *args).is_a?(Lazy) # Nothing to do if already backported, since it would use to_enum...
module_eval <<-EOT, __FILE__, __LINE__ + 1
def #{method}(*args) # def cycle(*args)
return to_enum(:#{method}, *args) unless block_given? # return to_enum(:cycle, *args) unless block_given?
super # super
end # end
EOT
end
end
def chunk(*)
super.lazy
end if Enumerable.method_defined?(:chunk) && ![].lazy.chunk{}.is_a?(Lazy)
def map
raise ArgumentError, "tried to call lazy map without a block" unless block_given?
Lazy.new(self) do |yielder, *values|
yielder << yield(*values)
end.__set_inspect :map
end
alias_method :collect, :map
def select
raise ArgumentError, "tried to call lazy select without a block" unless block_given?
Lazy.new(self) do |yielder, *values|
values = values.first unless values.size > 1
yielder.yield values if yield values
end.__set_inspect :select
end
alias_method :find_all, :select
def reject
raise ArgumentError, "tried to call lazy reject without a block" unless block_given?
Lazy.new(self) do |yielder, *values|
values = values.first unless values.size > 1
yielder.yield(values) unless yield values
end.__set_inspect :reject
end
def grep(pattern)
if block_given?
# Split for performance
Lazy.new(self) do |yielder, *values|
values = values.first unless values.size > 1
yielder.yield(yield(values)) if pattern === values
end
else
Lazy.new(self) do |yielder, *values|
values = values.first unless values.size > 1
yielder.yield(values) if pattern === values
end
end.__set_inspect :grep, [pattern]
end
def drop(n)
n = Backports::coerce_to_int(n)
Lazy.new(self) do |yielder, *values|
data = yielder.backports_memo ||= {:remain => n}
if data[:remain] > 0
data[:remain] -= 1
else
yielder.yield(*values)
end
end.__set_inspect :drop, [n]
end
def drop_while
raise ArgumentError, "tried to call lazy drop_while without a block" unless block_given?
Lazy.new(self) do |yielder, *values|
data = yielder.backports_memo ||= {:dropping => true}
yielder.yield(*values) unless data[:dropping] &&= yield(*values)
end.__set_inspect :drop_while
end
def take(n)
n = Backports::coerce_to_int(n)
raise ArgumentError, 'attempt to take negative size' if n < 0
Lazy.new(n == 0 ? [] : self) do |yielder, *values|
data = yielder.backports_memo ||= {:remain => n}
yielder.yield(*values)
throw @@done if (data[:remain] -= 1) == 0
end.__set_inspect :take, [n], self
end
def take_while
raise ArgumentError, "tried to call lazy take_while without a block" unless block_given?
Lazy.new(self) do |yielder, *values|
throw @@done unless yield(*values)
yielder.yield(*values)
end.__set_inspect :take_while
end
def flat_map
raise ArgumentError, "tried to call lazy flat_map without a block" unless block_given?
Lazy.new(self) do |yielder, *values|
result = yield(*values)
ary = Backports.is_array?(result)
if ary || (result.respond_to?(:each) && result.respond_to?(:force))
(ary || result).each{|x| yielder << x }
else
yielder << result
end
end.__set_inspect :flat_map
end
alias_method :collect_concat, :flat_map
def zip(*args)
return super if block_given?
arys = args.map{ |arg| Backports.is_array?(arg) }
if arys.all?
# Handle trivial case of multiple array arguments separately
# by avoiding Enumerator#next for efficiency & compatibility
Lazy.new(self) do |yielder, *values|
data = yielder.backports_memo ||= {:iter => 0}
values = values.first unless values.size > 1
yielder << arys.map{|ary| ary[data[:iter]]}.unshift(values)
data[:iter] += 1
end
else
args.each do |a|
raise TypeError, "wrong argument type #{a.class} (must respond to :each)" unless a.respond_to? :each
end
Lazy.new(self) do |yielder, *values|
enums = yielder.backports_memo ||= args.map(&:to_enum)
values = values.first unless values.size > 1
others = enums.map do |arg|
begin
arg.next
rescue StopIteration
nil
end
end
yielder << others.unshift(values)
end
end.__set_inspect :zip, args
end
protected
def __set_inspect(method, args = nil, receiver = nil)
@method = method
@args = args
@receiver = receiver if receiver
self
end
end
end
end
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