* ext/bigdecimal/lib/bigdecimal/util.rb (Rational#to_d):

  zero or negative precision is error.  fixes #5098.
  [ruby-dev:44210]
* test/bigdecimal/test_bigdecimal_util.rb: add test for the above
  change.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32680 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 29 insertions, 5 deletions

diff --git a/ChangeLog b/ChangeLog
index 93ab0121b7..d4dc2971a4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Wed Jul 27 00:50:00 2011  Kenta Murata  <mrkn@mrkn.jp>
+
+	* ext/bigdecimal/lib/bigdecimal/util.rb (Rational#to_d):
+	  zero or negative precision is error.  fixes #5098.
+	  [ruby-dev:44210]
+
+	* test/bigdecimal/test_bigdecimal_util.rb: add test for the above
+	  change.
+
 Wed Jul 27 00:48:00 2011  Kenta Murata  <mrkn@mrkn.jp>
 
 	* ext/bigdecimal/lib/bigdecimal/util.rb (Float#to_d): modified for
diff --git a/ext/bigdecimal/lib/bigdecimal/util.rb b/ext/bigdecimal/lib/bigdecimal/util.rb
index 1e4bbbb596..b27e64c511 100644
--- a/ext/bigdecimal/lib/bigdecimal/util.rb
+++ b/ext/bigdecimal/lib/bigdecimal/util.rb
@@ -95,11 +95,11 @@ class Rational < Numeric
   #   # => #<BigDecimal:1a52bd8,'0.3142857142 8571427937 0154144999 105E1',45(63)>
   #   r.to_d(3)
   #   # => #<BigDecimal:1a44d08,'0.314E1',18(36)>
-  def to_d(nFig=0)
-    num = self.numerator.to_s
-    if nFig<=0
-      nFig = BigDecimal.double_fig*2+1
+  def to_d(precision)
+    if precision <= 0
+      raise ArgumentError, "negative precision"
     end
-    BigDecimal.new(num).div(self.denominator,nFig)
+    num = self.numerator
+    BigDecimal(num).div(self.denominator, precision)
   end
 end
diff --git a/test/bigdecimal/test_bigdecimal_util.rb b/test/bigdecimal/test_bigdecimal_util.rb
index 87b4f20e99..72342b922f 100644
--- a/test/bigdecimal/test_bigdecimal_util.rb
+++ b/test/bigdecimal/test_bigdecimal_util.rb
@@ -25,4 +25,19 @@ class TestBigDecimalUtil < Test::Unit::TestCase
     assert_in_delta(BigDecimal(0.5, 5), 0.5.to_d(digits), delta)
     assert_in_delta(BigDecimal(355.0/113.0, 5), (355.0/113.0).to_d(digits), delta)
   end
+
+  def test_Rational_to_d
+    digits = 100
+    delta = 1.0/10**(digits)
+    assert_in_delta(BigDecimal(1.quo(2), digits), 1.quo(2).to_d(digits), delta)
+    assert_in_delta(BigDecimal(355.quo(113), digits), 355.quo(113).to_d(digits), delta)
+  end
+
+  def test_Rational_to_d_with_zero_precision
+    assert_raise(ArgumentError) { 355.quo(113).to_d(0) }
+  end
+
+  def test_Rational_to_d_with_negative_precision
+    assert_raise(ArgumentError) { 355.quo(113).to_d(-42) }
+  end
 end