Add `Enumerator.produce` from Ruby2.7
MODIFY
mrbgems/mruby-enumerator/mrblib/enumerator.rb
mrbgems/mruby-enumerator/mrblib/enumerator.rb
@@ -556,6 +556,42 @@ class Enumerator
self
end
end
+
+ ##
+ # call-seq:
+ # Enumerator.produce(initial = nil) { |val| } -> enumerator
+ #
+ # Creates an infinite enumerator from any block, just called over and
+ # over. Result of the previous iteration is passed to the next one.
+ # If +initial+ is provided, it is passed to the first iteration, and
+ # becomes the first element of the enumerator; if it is not provided,
+ # first iteration receives +nil+, and its result becomes first
+ # element of the iterator.
+ #
+ # Raising StopIteration from the block stops an iteration.
+ #
+ # Examples of usage:
+ #
+ # Enumerator.produce(1, &:succ) # => enumerator of 1, 2, 3, 4, ....
+ #
+ # Enumerator.produce { rand(10) } # => infinite random number sequence
+ #
+ # ancestors = Enumerator.produce(node) { |prev| node = prev.parent or raise StopIteration }
+ # enclosing_section = ancestors.find { |n| n.type == :section }
+ def Enumerator.produce(init=NONE, &block)
+ raise ArgumentError, "no block given" if block.nil?
+ Enumerator.new do |y|
+ if init == NONE
+ val = nil
+ else
+ val = init
+ y.yield(val)
+ end
+ loop do
+ y.yield(val = block.call(val))
+ end
+ end
+ end
end
module Kernel

MODIFY
mrbgems/mruby-enumerator/test/enumerator.rb
mrbgems/mruby-enumerator/test/enumerator.rb
@@ -10,9 +10,9 @@ def assert_take(exp, enumerator)
result = []
n = exp.size
enumerator.each do |v|
- break if n == 0
result << v
n -= 1
+ break if n == 0
end
assert_equal exp, result
end
@@ -560,3 +560,41 @@ assert 'Enumerable#zip' do
assert_raise(TypeError) { [1].zip(1) }
end
+
+assert 'Enumerator.produce' do
+ assert_raise(ArgumentError) { Enumerator.produce }
+
+ # Without initial object
+ passed_args = []
+ enum = Enumerator.produce {|obj| passed_args << obj; (obj || 0).succ }
+ assert_equal Enumerator, enum.class
+ assert_take [1, 2, 3], enum
+ assert_equal [nil, 1, 2], passed_args
+
+ # With initial object
+ passed_args = []
+ enum = Enumerator.produce(1) {|obj| passed_args << obj; obj.succ }
+ assert_take [1, 2, 3], enum
+ assert_equal [1, 2], passed_args
+
+ # Raising StopIteration
+ words = %w[The quick brown fox jumps over the lazy dog]
+ enum = Enumerator.produce { words.shift or raise StopIteration }
+ assert_equal %w[The quick brown fox jumps over the lazy dog], enum.to_a
+
+ # Raising StopIteration
+ object = [[[["abc", "def"], "ghi", "jkl"], "mno", "pqr"], "stuv", "wxyz"]
+ enum = Enumerator.produce(object) {|obj|
+ obj.respond_to?(:first) or raise StopIteration
+ obj.first
+ }
+ assert_nothing_raised {
+ assert_equal [
+ [[[["abc", "def"], "ghi", "jkl"], "mno", "pqr"], "stuv", "wxyz"],
+ [[["abc", "def"], "ghi", "jkl"], "mno", "pqr"],
+ [["abc", "def"], "ghi", "jkl"],
+ ["abc", "def"],
+ "abc",
+ ], enum.to_a
+ }
+end

Add `Enumerator.produce` from Ruby2.7