diff options
-rw-r--r-- | math.c | 9 | ||||
-rw-r--r-- | test/ruby/test_math.rb | 1 |
2 files changed, 9 insertions, 1 deletions
@@ -689,7 +689,14 @@ rb_math_sqrt(VALUE x) static VALUE math_cbrt(VALUE unused_obj, VALUE x) { - return DBL2NUM(cbrt(Get_Double(x))); + double f = Get_Double(x); + double r = cbrt(f); +#if defined __GLIBC__ + if (isfinite(r)) { + r = (2.0 * r + (f / r / r)) / 3.0; + } +#endif + return DBL2NUM(r); } /* diff --git a/test/ruby/test_math.rb b/test/ruby/test_math.rb index f226287442..5cc12bcfeb 100644 --- a/test/ruby/test_math.rb +++ b/test/ruby/test_math.rb @@ -202,6 +202,7 @@ class TestMath < Test::Unit::TestCase check(3, Math.cbrt(27)) check(-0.1, Math.cbrt(-0.001)) assert_nothing_raised { assert_infinity(Math.cbrt(1.0/0)) } + assert_operator(Math.cbrt(1.0 - Float::EPSILON), :<=, 1.0) end def test_frexp |