mame	2018-04-04 23:02:59 +0900 (Wed, 04 Apr 2018)

  New Revision: 63093

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=63093

  Log:
    bignum.c: Bignum#fdiv avoids double division when divisor is bignum
    
    `Rational(int, bignum).to_f` sometimes returned a wrong result because
    `Bignum#div` casted its divisor to double.  [Bug #14637] [ruby-core:86330]

  Modified files:
    trunk/bignum.c
    trunk/test/ruby/test_rational.rb
Index: bignum.c
===================================================================
--- bignum.c	(revision 63092)
+++ bignum.c	(revision 63093)
@@ -6178,9 +6178,7 @@ rb_big_fdiv_double(VALUE x, VALUE y) https://github.com/ruby/ruby/blob/trunk/bignum.c#L6178
 	    return big_fdiv_int(x, rb_int2big(FIX2LONG(y)));
     }
     else if (RB_BIGNUM_TYPE_P(y)) {
-	dy = rb_big2dbl(y);
-	if (isinf(dx) || isinf(dy))
-	    return big_fdiv_int(x, y);
+	return big_fdiv_int(x, y);
     }
     else if (RB_FLOAT_TYPE_P(y)) {
 	dy = RFLOAT_VALUE(y);
Index: test/ruby/test_rational.rb
===================================================================
--- test/ruby/test_rational.rb	(revision 63092)
+++ test/ruby/test_rational.rb	(revision 63093)
@@ -837,6 +837,7 @@ class Rational_Test < Test::Unit::TestCa https://github.com/ruby/ruby/blob/trunk/test/ruby/test_rational.rb#L837
   def test_to_f
     assert_equal(1.5, Rational(3,2).to_f)
     assert_equal(1.5, Float(Rational(3,2)))
+    assert_equal(1e-23, Rational(1, 10**23).to_f, "Bug #14637")
   end
 
   def test_to_c

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