numeric.c: Fix negative step with float components

* numeric.c (ruby_float_step): fix negative step with float components.

* test/ruby/test_numeric.c (test_step_bug15537): add tests.

* test/ruby/test_range.c (test_step_bug15537): add tests.

[Bug #15537] [ruby-core:91101]

From: shuujii (Shuji KOBAYASHI) <shuujii@gmail.com>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66914 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 21 insertions, 2 deletions

diff --git a/numeric.c b/numeric.c
index 5cb1aad8a1..896d667cf8 100644
--- a/numeric.c
+++ b/numeric.c
@@ -2514,9 +2514,9 @@ int
 ruby_float_step(VALUE from, VALUE to, VALUE step, int excl, int allow_endless)
 {
     if (RB_TYPE_P(from, T_FLOAT) || RB_TYPE_P(to, T_FLOAT) || RB_TYPE_P(step, T_FLOAT)) {
-	double beg = NUM2DBL(from);
-	double end = (allow_endless && NIL_P(to)) ? HUGE_VAL : NUM2DBL(to);
 	double unit = NUM2DBL(step);
+	double beg = NUM2DBL(from);
+	double end = (allow_endless && NIL_P(to)) ? (unit < 0 ? -1 : 1)*HUGE_VAL : NUM2DBL(to);
 	double n = ruby_float_step_size(beg, end, unit, excl);
 	long i;
 
diff --git a/test/ruby/test_numeric.rb b/test/ruby/test_numeric.rb
index e48c3448e8..f48bce5411 100644
--- a/test/ruby/test_numeric.rb
+++ b/test/ruby/test_numeric.rb
@@ -339,6 +339,20 @@ class TestNumeric < Test::Unit::TestCase
     assert_step [bignum]*4, [bignum, by: 0, to: 0], inf: true
   end
 
+  def test_step_bug15537
+    assert_step [10.0, 8.0, 6.0, 4.0, 2.0], [10.0, 1, -2]
+    assert_step [10.0, 8.0, 6.0, 4.0, 2.0], [10.0, to: 1, by: -2]
+    assert_step [10.0, 8.0, 6.0, 4.0, 2.0], [10.0, 1, -2]
+    assert_step [10.0, 8.0, 6.0, 4.0, 2.0], [10, to: 1.0, by: -2]
+    assert_step [10.0, 8.0, 6.0, 4.0, 2.0], [10, 1.0, -2]
+
+    assert_step [10.0, 9.0, 8.0, 7.0], [10, by: -1.0], inf: true
+    assert_step [10.0, 9.0, 8.0, 7.0], [10, by: -1.0, to: nil], inf: true
+    assert_step [10.0, 9.0, 8.0, 7.0], [10, nil, -1.0], inf: true
+    assert_step [10.0, 9.0, 8.0, 7.0], [10.0, by: -1], inf: true
+    assert_step [10.0, 9.0, 8.0, 7.0], [10.0, nil, -1], inf: true
+  end
+
   def test_num2long
     assert_raise(TypeError) { 1 & nil }
     assert_raise(TypeError) { 1 & 1.0 }
diff --git a/test/ruby/test_range.rb b/test/ruby/test_range.rb
index 65f3a8974d..6a2081fcd2 100644
--- a/test/ruby/test_range.rb
+++ b/test/ruby/test_range.rb
@@ -322,6 +322,11 @@ class TestRange < Test::Unit::TestCase
     assert_equal(["a", "b", "c"], a)
   end
 
+  def test_step_bug15537
+    assert_equal([10.0, 9.0, 8.0, 7.0], (10 ..).step(-1.0).take(4))
+    assert_equal([10.0, 9.0, 8.0, 7.0], (10.0 ..).step(-1).take(4))
+  end
+
   def test_percent_step
     aseq = (1..10) % 2
     assert_equal(Enumerator::ArithmeticSequence, aseq.class)