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numeric.c: float_invariant_round

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* numeric.c (float_invariant_round): extracted from flo_round to
  be optimizer-friendly, e.g., tail-call optimization.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54554 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
nobu 2016-04-13 02:41:24 +00:00
parent 456523e2ed
commit aaf0f51f46
1 changed files with 16 additions and 6 deletions
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22
numeric.c
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@ -110,6 +110,7 @@ static VALUE fix_rshift(long, unsigned long);
static VALUE int_pow(long x, unsigned long y); static VALUE int_pow(long x, unsigned long y);
static VALUE int_cmp(VALUE x, VALUE y); static VALUE int_cmp(VALUE x, VALUE y);
static VALUE flo_truncate(VALUE num); static VALUE flo_truncate(VALUE num);
static int float_invariant_round(double number, int ndigits, VALUE *num);
static ID id_coerce, id_div, id_divmod; static ID id_coerce, id_div, id_divmod;
#define id_to_i idTo_i #define id_to_i idTo_i
@ -1840,8 +1841,6 @@ flo_round(int argc, VALUE *argv, VALUE num)
{ {
double number, f; double number, f;
int ndigits = 0; int ndigits = 0;
int binexp;
enum {float_dig = DBL_DIG+2};
if (rb_check_arity(argc, 0, 1)) { if (rb_check_arity(argc, 0, 1)) {
ndigits = NUM2INT(argv[0]); ndigits = NUM2INT(argv[0]);
@ -1853,6 +1852,17 @@ flo_round(int argc, VALUE *argv, VALUE num)
if (ndigits == 0) { if (ndigits == 0) {
return dbl2ival(round(number)); return dbl2ival(round(number));
} }
if (float_invariant_round(number, ndigits, &num)) return num;
f = pow(10, ndigits);
return DBL2NUM(round(number * f) / f);
}
static int
float_invariant_round(double number, int ndigits, VALUE *num)
{
enum {float_dig = DBL_DIG+2};
int binexp;
frexp(number, &binexp); frexp(number, &binexp);
/* Let `exp` be such that `number` is written as:"0.#{digits}e#{exp}", /* Let `exp` be such that `number` is written as:"0.#{digits}e#{exp}",
@ -1874,13 +1884,13 @@ flo_round(int argc, VALUE *argv, VALUE num)
*/ */
if (isinf(number) || isnan(number) || if (isinf(number) || isnan(number) ||
(ndigits >= float_dig - (binexp > 0 ? binexp / 4 : binexp / 3 - 1))) { (ndigits >= float_dig - (binexp > 0 ? binexp / 4 : binexp / 3 - 1))) {
return num; return TRUE;
} }
if (ndigits < - (binexp > 0 ? binexp / 3 + 1 : binexp / 4)) { if (ndigits < - (binexp > 0 ? binexp / 3 + 1 : binexp / 4)) {
return DBL2NUM(0); *num = DBL2NUM(0);
return TRUE;
} }
f = pow(10, ndigits); return FALSE;
return DBL2NUM(round(number * f) / f);
} }
/* /*