numeric.c: round to nearest even

* numeric.c (flo_round, int_round): support round-to-nearest-even
  semantics of IEEE 754 to match sprintf behavior, and add `half:`
  optional keyword argument for the old behavior.
  [ruby-core:76273] [Bug #12548]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56590 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 42 insertions, 0 deletions

diff --git a/test/ruby/test_float.rb b/test/ruby/test_float.rb
index b31c0415f2..f2989e4f5b 100644
--- a/test/ruby/test_float.rb
+++ b/test/ruby/test_float.rb
@@ -659,6 +659,48 @@ class TestFloat < Test::Unit::TestCase
     }
   end
 
+  def test_round_half_even
+    assert_equal(12.0, 12.5.round(half: :even))
+    assert_equal(14.0, 13.5.round(half: :even))
+
+    assert_equal(2.2, 2.15.round(1, half: :even))
+    assert_equal(2.2, 2.25.round(1, half: :even))
+    assert_equal(2.4, 2.35.round(1, half: :even))
+
+    assert_equal(-2.2, -2.15.round(1, half: :even))
+    assert_equal(-2.2, -2.25.round(1, half: :even))
+    assert_equal(-2.4, -2.35.round(1, half: :even))
+
+    assert_equal(7.1364, 7.13645.round(4, half: :even))
+    assert_equal(7.1365, 7.1364501.round(4, half: :even))
+    assert_equal(7.1364, 7.1364499.round(4, half: :even))
+
+    assert_equal(-7.1364, -7.13645.round(4, half: :even))
+    assert_equal(-7.1365, -7.1364501.round(4, half: :even))
+    assert_equal(-7.1364, -7.1364499.round(4, half: :even))
+  end
+
+  def test_round_half_up
+    assert_equal(13.0, 12.5.round(half: :up))
+    assert_equal(14.0, 13.5.round(half: :up))
+
+    assert_equal(2.2, 2.15.round(1, half: :up))
+    assert_equal(2.3, 2.25.round(1, half: :up))
+    assert_equal(2.4, 2.35.round(1, half: :up))
+
+    assert_equal(-2.2, -2.15.round(1, half: :up))
+    assert_equal(-2.3, -2.25.round(1, half: :up))
+    assert_equal(-2.4, -2.35.round(1, half: :up))
+
+    assert_equal(7.1365, 7.13645.round(4, half: :up))
+    assert_equal(7.1365, 7.1364501.round(4, half: :up))
+    assert_equal(7.1364, 7.1364499.round(4, half: :up))
+
+    assert_equal(-7.1365, -7.13645.round(4, half: :up))
+    assert_equal(-7.1365, -7.1364501.round(4, half: :up))
+    assert_equal(-7.1364, -7.1364499.round(4, half: :up))
+  end
+
   def test_Float
     assert_in_delta(0.125, Float("0.1_2_5"), 0.00001)
     assert_in_delta(0.125, "0.1_2_5__".to_f, 0.00001)