* numeric.c (flo_round): substitute machine dependent magic number.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@33158 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 23 insertions, 5 deletions

diff --git a/ChangeLog b/ChangeLog
index 58c5477271..0a1909ee1d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Sep  2 01:07:14 2011  Nobuyoshi Nakada  <[email protected]>
+
+	* numeric.c (flo_round): substitute machine dependent magic number.
+
 Thu Sep  1 17:31:22 2011  Nobuyoshi Nakada  <[email protected]>
 
 	* insns.def (defineclass), vm_insnhelper.c (vm_get_cvar_base): see
diff --git a/numeric.c b/numeric.c
index 176b589b0b..201dfabd28 100644
--- a/numeric.c
+++ b/numeric.c
@@ -1493,17 +1493,18 @@ flo_round(int argc, VALUE *argv, VALUE num)
     int ndigits = 0;
     int binexp;
     long val;
+    enum {float_dig = DBL_DIG+2};
 
     if (argc > 0 && rb_scan_args(argc, argv, "01", &nd) == 1) {
 	ndigits = NUM2INT(nd);
     }
     number  = RFLOAT_VALUE(num);
-    frexp (number , &binexp);
+    frexp(number, &binexp);
 
 /* Let `exp` be such that `number` is written as:"0.#{digits}e#{exp}",
    i.e. such that  10 ** (exp - 1) <= |number| < 10 ** exp
-   Recall that up to 17 digits can be needed to represent a double,
-   so if ndigits + exp >= 17, the intermediate value (number * 10 ** ndigits)
+   Recall that up to float_dig digits can be needed to represent a double,
+   so if ndigits + exp >= float_dig, the intermediate value (number * 10 ** ndigits)
    will be an integer and thus the result is the original number.
    If ndigits + exp <= 0, the result is 0 or "1e#{exp}", so
    if ndigits + exp < 0, the result is 0.
@@ -1514,7 +1515,7 @@ flo_round(int argc, VALUE *argv, VALUE num)
 	   10 ** (binexp/4 - 1) < |number| < 10 ** (binexp/3)
 	   binexp/4 <= exp <= binexp/3
 	If binexp <= 0, swap the /4 and the /3
-	So if ndigits + binexp/(4 or 3) >= 17, the result is number
+	So if ndigits + binexp/(4 or 3) >= float_dig, the result is number
 	If ndigits + binexp/(3 or 4) < 0 the result is 0
 */
     if (isinf(number) || isnan(number)) {
@@ -1523,7 +1524,7 @@ flo_round(int argc, VALUE *argv, VALUE num)
     else if ((long)ndigits * (4 - (binexp > 0)) + binexp < 0) {
 	number = 0;
     }
-    else if (((long)ndigits - 17) * (3 + (binexp > 0)) + binexp < 0) {
+    else if (((long)ndigits - float_dig) * (3 + (binexp > 0)) + binexp < 0) {
 	f = pow(10, abs(ndigits));
 	if (ndigits < 0) {
 	    double absnum = fabs(number);
diff --git a/test/ruby/test_float.rb b/test/ruby/test_float.rb
index fb37d73831..c244447bd7 100644
--- a/test/ruby/test_float.rb
+++ b/test/ruby/test_float.rb
@@ -315,7 +315,9 @@ class TestFloat < Test::Unit::TestCase
     assert_raise(FloatDomainError) { inf.ceil }
     assert_raise(FloatDomainError) { inf.round }
     assert_raise(FloatDomainError) { inf.truncate }
+  end
 
+  def test_round_with_precision
     assert_equal(1.100, 1.111.round(1))
     assert_equal(1.110, 1.111.round(2))
     assert_equal(11110.0, 11111.1.round(-1))
@@ -323,6 +325,17 @@ class TestFloat < Test::Unit::TestCase
 
     assert_equal(10**300, 1.1e300.round(-300))
     assert_equal(-10**300, -1.1e300.round(-300))
+    assert_equal(1.0e-300, 1.1e-300.round(300))
+    assert_equal(-1.0e-300, -1.1e-300.round(300))
+
+    bug5227 = '[ruby-core:39093]'
+    assert_equal(42.0, 42.0.round(308), bug5227)
+    assert_equal(1.0e307, 1.0e307.round(2), bug5227)
+
+    assert_raise(TypeError) {1.0.round("4")}
+    assert_raise(TypeError) {1.0.round(nil)}
+    def (prec = Object.new).to_int; 2; end
+    assert_equal(1.0, 0.998.round(prec))
   end
 
   VS = [