diff options
| -rw-r--r-- | numeric.c | 22 |
1 files changed, 16 insertions, 6 deletions
@@ -110,6 +110,7 @@ static VALUE fix_rshift(long, unsigned long); static VALUE int_pow(long x, unsigned long y); static VALUE int_cmp(VALUE x, VALUE y); 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; #define id_to_i idTo_i @@ -1840,8 +1841,6 @@ flo_round(int argc, VALUE *argv, VALUE num) { double number, f; int ndigits = 0; - int binexp; - enum {float_dig = DBL_DIG+2}; if (rb_check_arity(argc, 0, 1)) { ndigits = NUM2INT(argv[0]); @@ -1853,6 +1852,17 @@ flo_round(int argc, VALUE *argv, VALUE num) if (ndigits == 0) { 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); /* 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) || (ndigits >= float_dig - (binexp > 0 ? binexp / 4 : binexp / 3 - 1))) { - return num; + return TRUE; } if (ndigits < - (binexp > 0 ? binexp / 3 + 1 : binexp / 4)) { - return DBL2NUM(0); + *num = DBL2NUM(0); + return TRUE; } - f = pow(10, ndigits); - return DBL2NUM(round(number * f) / f); + return FALSE; } /* |