Fix Enumerator::ArithmeticSequence handling of float ranges

Depending on the float range, there could be an off-by-one error,
where the last result that should be in the range was missed. Fix
this by checking if the computed value for the expected value
outside the range is still inside the range, and if so, increment
the step size.

Fixes [Bug #16612]

3 files changed, 50 insertions, 19 deletions

diff --git a/numeric.c b/numeric.c
index 17a401f7d7..d0538ca126 100644
--- a/numeric.c
+++ b/numeric.c
@@ -2409,11 +2409,11 @@ ruby_float_step_size(double beg, double end, double unit, int excl)
     if (unit == 0) {
         return HUGE_VAL;
     }
-    n= (end - beg)/unit;
-    err = (fabs(beg) + fabs(end) + fabs(end-beg)) / fabs(unit) * epsilon;
     if (isinf(unit)) {
 	return unit > 0 ? beg <= end : beg >= end;
     }
+    n= (end - beg)/unit;
+    err = (fabs(beg) + fabs(end) + fabs(end-beg)) / fabs(unit) * epsilon;
     if (err>0.5) err=0.5;
     if (excl) {
 	if (n<=0) return 0;
@@ -2421,10 +2421,26 @@ ruby_float_step_size(double beg, double end, double unit, int excl)
 	    n = 0;
 	else
 	    n = floor(n - err);
+        if (beg < end) {
+            if ((n+1)*unit+beg < end)
+                n++;
+        }
+        else if (beg > end) {
+            if ((n+1)*unit+beg > end)
+                n++;
+        }
     }
     else {
 	if (n<0) return 0;
 	n = floor(n + err);
+        if (beg < end) {
+            if ((n+1)*unit+beg <= end)
+                n++;
+        }
+        else if (beg > end) {
+            if ((n+1)*unit+beg >= end)
+               n++;
+        }
     }
     return n+1;
 }
diff --git a/spec/ruby/core/range/step_spec.rb b/spec/ruby/core/range/step_spec.rb
index e284551ab3..1c2e30742c 100644
--- a/spec/ruby/core/range/step_spec.rb
+++ b/spec/ruby/core/range/step_spec.rb
@@ -207,10 +207,12 @@ describe "Range#step" do
         ScratchPad.recorded.should eql([-1.0, -0.5, 0.0, 0.5])
       end
 
-      it "returns Float values of 'step * n + begin < end'" do
-        (1.0...6.4).step(1.8) { |x| ScratchPad << x }
-        (1.0...55.6).step(18.2) { |x| ScratchPad << x }
-        ScratchPad.recorded.should eql([1.0, 2.8, 4.6, 1.0, 19.2, 37.4])
+      ruby_version_is '3.1' do
+        it "returns Float values of 'step * n + begin < end'" do
+          (1.0...6.4).step(1.8) { |x| ScratchPad << x }
+          (1.0...55.6).step(18.2) { |x| ScratchPad << x }
+          ScratchPad.recorded.should eql([1.0, 2.8, 4.6, 1.0, 19.2, 37.4, 55.599999999999994])
+        end
       end
 
       it "handles infinite values at either end" do
@@ -457,19 +459,21 @@ describe "Range#step" do
           (-1.0...1.0).step(0.5).size.should == 4
         end
 
-        it "returns the range size when there's no step_size" do
-          (-2..2).step.size.should == 5
-          (-2.0..2.0).step.size.should == 5
-          (-2..2.0).step.size.should == 5
-          (-2.0..2).step.size.should == 5
-          (1.0..6.4).step(1.8).size.should == 4
-          (1.0..12.7).step(1.3).size.should == 10
-          (-2...2).step.size.should == 4
-          (-2.0...2.0).step.size.should == 4
-          (-2...2.0).step.size.should == 4
-          (-2.0...2).step.size.should == 4
-          (1.0...6.4).step(1.8).size.should == 3
-          (1.0...55.6).step(18.2).size.should == 3
+        ruby_version_is '3.1' do
+          it "returns the range size when there's no step_size" do
+            (-2..2).step.size.should == 5
+            (-2.0..2.0).step.size.should == 5
+            (-2..2.0).step.size.should == 5
+            (-2.0..2).step.size.should == 5
+            (1.0..6.4).step(1.8).size.should == 4
+            (1.0..12.7).step(1.3).size.should == 10
+            (-2...2).step.size.should == 4
+            (-2.0...2.0).step.size.should == 4
+            (-2...2.0).step.size.should == 4
+            (-2.0...2).step.size.should == 4
+            (1.0...6.4).step(1.8).size.should == 3
+            (1.0...55.6).step(18.2).size.should == 4
+          end
         end
 
         it "returns nil with begin and end are String" do
diff --git a/test/ruby/test_float.rb b/test/ruby/test_float.rb
index fbf0d87f8e..ca616456f1 100644
--- a/test/ruby/test_float.rb
+++ b/test/ruby/test_float.rb
@@ -882,6 +882,11 @@ class TestFloat < Test::Unit::TestCase
     end
 
     assert_equal([5.0, 4.0, 3.0, 2.0], 5.0.step(1.5, -1).to_a)
+
+    assert_equal(11, ((0.24901079128550474)..(340.2500808898068)).step(34.00010700985213).to_a.size)
+    assert_equal(11, ((0.24901079128550474)..(340.25008088980684)).step(34.00010700985213).to_a.size)
+    assert_equal(11, ((-0.24901079128550474)..(-340.2500808898068)).step(-34.00010700985213).to_a.size)
+    assert_equal(11, ((-0.24901079128550474)..(-340.25008088980684)).step(-34.00010700985213).to_a.size)
   end
 
   def test_step2
@@ -893,6 +898,7 @@ class TestFloat < Test::Unit::TestCase
       a = rand
       b = a+rand*1000
       s = (b - a) / 10
+      b = a + s*10
       seq = (a...b).step(s)
       assert_equal(10, seq.to_a.length, seq.inspect)
     end
@@ -903,6 +909,11 @@ class TestFloat < Test::Unit::TestCase
     (1.0 ... e).step(1E-16) do |n|
       assert_operator(n, :<=, e)
     end
+
+    assert_equal(10, ((0.24901079128550474)...(340.2500808898068)).step(34.00010700985213).to_a.size)
+    assert_equal(11, ((0.24901079128550474)...(340.25008088980684)).step(34.00010700985213).to_a.size)
+    assert_equal(10, ((-0.24901079128550474)...(-340.2500808898068)).step(-34.00010700985213).to_a.size)
+    assert_equal(11, ((-0.24901079128550474)...(-340.25008088980684)).step(-34.00010700985213).to_a.size)
   end
 
   def test_singleton_method