From: Andy Moreton <andrewjmoreton@gmail.com>
To: emacs-devel@gnu.org
Subject: Re: Merging bignum to master
Date: Thu, 16 Aug 2018 00:41:32 +0100 [thread overview]
Message-ID: <86sh3fgpub.fsf@gmail.com> (raw)
In-Reply-To: 86r2j13ihs.fsf@gmail.com
On Tue 14 Aug 2018, Andy Moreton wrote:
> On Sun 12 Aug 2018, Tom Tromey wrote:
>
>>>>>>> "Basil" == Basil L Contovounesios <contovob@tcd.ie> writes:
>>
>> Basil> It'd be nice if expt could be updated to handle bignums:
>>
>> What do you think of this?
Tom and Basil, please try the following patch for expt.
I have given it some light sanity testing on Windows 64bit.
AndyM
diff --git a/src/floatfns.c b/src/floatfns.c
index bbf7df4db3..0e7e3090e8 100644
--- a/src/floatfns.c
+++ b/src/floatfns.c
@@ -204,29 +204,38 @@ DEFUN ("expt", Fexpt, Sexpt, 2, 2, 0,
doc: /* Return the exponential ARG1 ** ARG2. */)
(Lisp_Object arg1, Lisp_Object arg2)
{
- CHECK_FIXNUM_OR_FLOAT (arg1);
+ CHECK_NUMBER (arg1);
CHECK_FIXNUM_OR_FLOAT (arg2);
- if (FIXNUMP (arg1) /* common lisp spec */
- && FIXNUMP (arg2) /* don't promote, if both are ints, and */
- && XFIXNUM (arg2) >= 0) /* we are sure the result is not fractional */
- { /* this can be improved by pre-calculating */
- EMACS_INT y; /* some binary powers of x then accumulating */
- EMACS_UINT acc, x; /* Unsigned so that overflow is well defined. */
- Lisp_Object val;
-
- x = XFIXNUM (arg1);
- y = XFIXNUM (arg2);
- acc = (y & 1 ? x : 1);
-
- while ((y >>= 1) != 0)
- {
- x *= x;
- if (y & 1)
- acc *= x;
- }
- XSETINT (val, acc);
- return val;
+
+ if (INTEGERP (arg1) /* common lisp spec */
+ && FIXNUMP (arg2) /* don't promote, if both are ints, and */
+ && XFIXNUM (arg2) >= 0 /* we are sure the result is not fractional */
+ && (sizeof (EMACS_INT) <= sizeof (long)
+ || (long) XFIXNUM (arg2) == XFIXNUM (arg2)))
+ {
+ Lisp_Object res;
+ mpz_t val;
+
+ mpz_init (val);
+ if (BIGNUMP (arg1))
+ {
+ mpz_pow_ui (val, XBIGNUM (arg1)->value, XFIXNUM (arg2));
+ }
+ else if (XFIXNUM (arg1) >= 0)
+ {
+ mpz_ui_pow_ui (val, XFIXNUM (arg1), XFIXNUM (arg2));
+ }
+ else
+ {
+ mpz_ui_pow_ui (val, -XFIXNUM (arg1), XFIXNUM (arg2));
+ if (XFIXNUM (arg2) & 1)
+ mpz_neg (val, val);
+ }
+ res = make_number (val);
+ mpz_clear (val);
+ return res;
}
+
return make_float (pow (XFLOATINT (arg1), XFLOATINT (arg2)));
}
next prev parent reply other threads:[~2018-08-15 23:41 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-11 19:47 Merging bignum to master Tom Tromey
2018-08-11 21:28 ` Basil L. Contovounesios
2018-08-12 16:34 ` Tom Tromey
2018-08-13 12:21 ` Basil L. Contovounesios
2018-08-14 0:21 ` Andy Moreton
2018-08-15 23:41 ` Andy Moreton [this message]
2018-08-16 15:38 ` Basil L. Contovounesios
2018-08-19 8:26 ` Paul Eggert
2018-08-17 14:58 ` Eli Zaretskii
2018-08-12 6:29 ` Ulrich Mueller
2018-08-12 8:09 ` Paul Eggert
2018-08-12 17:21 ` Ulrich Mueller
2018-08-12 18:20 ` Eli Zaretskii
2018-08-12 19:30 ` Ulrich Mueller
2018-08-13 0:15 ` Paul Eggert
2018-08-12 18:05 ` Eli Zaretskii
2018-08-12 23:53 ` Paul Eggert
2018-08-13 0:20 ` Tom Tromey
2018-08-13 7:51 ` Andreas Schwab
2018-08-13 8:06 ` Ulrich Mueller
2018-08-13 9:14 ` Paul Eggert
2018-08-14 23:09 ` Paul Eggert
2018-08-16 2:46 ` Richard Stallman
2018-08-13 23:31 ` Richard Stallman
2018-08-14 1:41 ` Paul Eggert
2018-08-16 2:41 ` Richard Stallman
2018-08-16 19:31 ` Paul Eggert
2018-08-16 22:02 ` Stefan Monnier
2018-08-12 7:37 ` John Wiegley
2018-08-12 18:21 ` Eli Zaretskii
2018-08-12 11:48 ` Pip Cet
2018-08-12 16:02 ` Tom Tromey
2018-08-13 22:58 ` Paul Eggert
2018-08-14 1:12 ` Noam Postavsky
2018-08-14 13:04 ` Pip Cet
2018-08-14 18:01 ` Paul Eggert
2018-08-15 15:20 ` Pip Cet
2018-08-15 16:17 ` Paul Eggert
2018-08-15 23:57 ` Andy Moreton
2018-08-16 22:00 ` Stefan Monnier
2018-08-20 16:28 ` Some vars now limited to fixnum size. (Was: Merging bignum to master) Karl Fogel
2018-08-20 16:54 ` Paul Eggert
2018-08-20 17:27 ` Eli Zaretskii
2018-08-20 17:27 ` Paul Eggert
2018-08-20 18:00 ` Eli Zaretskii
2018-08-20 19:55 ` Pip Cet
2018-08-20 23:15 ` Paul Eggert
2018-08-21 15:01 ` Some vars now limited to fixnum size Tom Tromey
2018-08-21 16:36 ` Andy Moreton
2018-08-21 18:46 ` Paul Eggert
2018-08-22 15:39 ` Tom Tromey
2018-08-21 3:38 ` Some vars now limited to fixnum size. (Was: Merging bignum to master) Richard Stallman
2018-08-21 4:09 ` Paul Eggert
2018-08-22 4:03 ` Richard Stallman
2018-08-22 4:53 ` Paul Eggert
2018-08-20 17:25 ` Eli Zaretskii
2018-08-14 0:51 ` Merging bignum to master Andy Moreton
2018-08-15 15:46 ` Andy Moreton
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