diff options
| -rw-r--r-- | Modules/_decimal/libmpdec/mpdecimal.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/Modules/_decimal/libmpdec/mpdecimal.c b/Modules/_decimal/libmpdec/mpdecimal.c index b21563a..1fc3cb9 100644 --- a/Modules/_decimal/libmpdec/mpdecimal.c +++ b/Modules/_decimal/libmpdec/mpdecimal.c @@ -4793,12 +4793,25 @@ mpd_qlog10(mpd_t *result, const mpd_t *a, const mpd_context_t *ctx, mpd_qfinalize(result, &workctx, status); return; } - /* Check if the result will overflow. + /* + * Check if the result will overflow (0 < x, x != 1): + * 1) log10(x) < 0 iff adjexp(x) < 0 + * 2) 0 < x /\ x <= y ==> adjexp(x) <= adjexp(y) + * 3) adjexp(x) <= log10(x) < adjexp(x) + 1 * - * 1) adjexp(a) + 1 > log10(a) >= adjexp(a) + * Case adjexp(x) >= 0: + * 4) adjexp(x) <= abs(log10(x)) + * Case adjexp(x) > 0: + * 5) adjexp(adjexp(x)) <= adjexp(abs(log10(x))) + * Case adjexp(x) == 0: + * mpd_exp_digits(t)-1 == 0 <= emax (the shortcut is not triggered) * - * 2) |log10(a)| >= adjexp(a), if adjexp(a) >= 0 - * |log10(a)| > -adjexp(a)-1, if adjexp(a) < 0 + * Case adjexp(x) < 0: + * 6) -adjexp(x) - 1 < abs(log10(x)) + * Case adjexp(x) < -1: + * 7) adjexp(-adjexp(x) - 1) <= adjexp(abs(log(x))) + * Case adjexp(x) == -1: + * mpd_exp_digits(t)-1 == 0 <= emax (the shortcut is not triggered) */ adjexp = mpd_adjexp(a); t = (adjexp < 0) ? -adjexp-1 : adjexp; |