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

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git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@33158 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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nobu 2011-09-01 16:07:16 +00:00
parent 43284b6bf8
commit c4eb2983ba
3 changed files with 23 additions and 5 deletions
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4
ChangeLog
View file

@ -1,3 +1,7 @@
Fri Sep 2 01:07:14 2011 Nobuyoshi Nakada <nobu@ruby-lang.org>
* numeric.c (flo_round): substitute machine dependent magic number.
Thu Sep 1 17:31:22 2011 Nobuyoshi Nakada <nobu@ruby-lang.org>
* insns.def (defineclass), vm_insnhelper.c (vm_get_cvar_base): see

11
numeric.c
View file

@ -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);

13
test/ruby/test_float.rb
View file

@ -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 = [