* numeric.c (flo_round): fix inaccurate results.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@31158 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Wed Mar 23 08:07:33 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* numeric.c (flo_round): fix inaccurate results.
+
 Wed Mar 23 00:12:16 2011  Tajima Akio <artonx@yahoo.co.jp>
 
 	* win32/win32.c: wait process real termination after reading 

include/ruby/intern.h

@@ -126,6 +126,7 @@ VALUE rb_big_plus(VALUE, VALUE);
 VALUE rb_big_minus(VALUE, VALUE);
 VALUE rb_big_mul(VALUE, VALUE);
 VALUE rb_big_div(VALUE, VALUE);
+VALUE rb_big_idiv(VALUE, VALUE);
 VALUE rb_big_modulo(VALUE, VALUE);
 VALUE rb_big_divmod(VALUE, VALUE);
 VALUE rb_big_pow(VALUE, VALUE);

numeric.c

@@ -97,6 +97,9 @@ round(double x)
 }
 #endif
 
+static VALUE fix_mul(VALUE x, VALUE y);
+static VALUE int_pow(long x, unsigned long y);
+
 static ID id_coerce, id_to_i, id_eq;
 
 VALUE rb_cNumeric;
@@ -1492,7 +1495,15 @@ flo_round(int argc, VALUE *argv, VALUE num)
 	if (ndigits < 0) number = 0;
     }
     else {
-	if (ndigits < 0) number /= f;
+	if (ndigits < 0) {
+	    if (fabs(number) < f) return INT2FIX(0);
+	    if (!FIXABLE(number)) {
+		VALUE f10 = int_pow(10, -ndigits);
+		num = rb_big_idiv(rb_dbl2big(number), f10);
+		return FIXNUM_P(num) ? fix_mul(num, f10) : rb_big_mul(num, f10);
+	    }
+	    number /= f;
+	}
 	else number *= f;
 	number = round(number);
 	if (ndigits < 0) number *= f;

test/ruby/test_float.rb

@@ -320,6 +320,8 @@ class TestFloat < Test::Unit::TestCase
     assert_equal(1.110, 1.111.round(2))
     assert_equal(11110.0, 11111.1.round(-1))
     assert_equal(11100.0, 11111.1.round(-2))
+
+    assert_equal(10**300, 1.1e300.round(-300))
   end
 
   VS = [