enumerator.c: Introduce Enumerator::ArithmeticSequence

This commit introduces new core class Enumerator::ArithmeticSequence.
Enumerator::ArithmeticSequence is a subclass of Enumerator, and
represents a number generator of an arithmetic sequence.

After this commit, Numeric#step and Range#step without blocks
returned an ArithmeticSequence object instead of an Enumerator.

This class introduces the following incompatibilities:

- You can create a zero-step ArithmeticSequence,
  and its size is not ArgumentError, but Infinity.
- You can create a negative-step ArithmeticSequence from a range.

[ruby-core:82816] [Feature #13904]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64205 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 5 insertions, 1 deletions

diff --git a/test/ruby/test_range.rb b/test/ruby/test_range.rb
index eada19cfb6..a845dc4929 100644
--- a/test/ruby/test_range.rb
+++ b/test/ruby/test_range.rb
@@ -222,7 +222,11 @@ class TestRange < Test::Unit::TestCase
     (0..).step(2) {|x| a << x; break if a.size == 10 }
     assert_equal([0, 2, 4, 6, 8, 10, 12, 14, 16, 18], a)
 
-    assert_raise(ArgumentError) { (0..10).step(-1) { } }
+    assert_kind_of(Enumerator::ArithmeticSequence, (0..10).step)
+    assert_kind_of(Enumerator::ArithmeticSequence, (0..10).step(2))
+    assert_kind_of(Enumerator::ArithmeticSequence, (0..10).step(0.5))
+    assert_kind_of(Enumerator::ArithmeticSequence, (10..0).step(-1))
+
     assert_raise(ArgumentError) { (0..10).step(0) { } }
     assert_raise(ArgumentError) { (0..).step(-1) { } }
     assert_raise(ArgumentError) { (0..).step(0) { } }