From: Tom Tromey <tom@tromey.com>
To: "Basil L. Contovounesios" <contovob@tcd.ie>
Cc: Tom Tromey <tom@tromey.com>, emacs-devel@gnu.org
Subject: Re: Merging bignum to master
Date: Sun, 12 Aug 2018 10:34:29 -0600 [thread overview]
Message-ID: <87a7prk0h6.fsf@tromey.com> (raw)
In-Reply-To: <87o9e8oaot.fsf@tcd.ie> (Basil L. Contovounesios's message of "Sun, 12 Aug 2018 00:28:02 +0300")
>>>>> "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
diff --git a/src/floatfns.c b/src/floatfns.c
index bbf7df4db3..c55418a35c 100644
--- a/src/floatfns.c
+++ b/src/floatfns.c
@@ -206,25 +206,28 @@ DEFUN ("expt", Fexpt, Sexpt, 2, 2, 0,
{
CHECK_FIXNUM_OR_FLOAT (arg1);
CHECK_FIXNUM_OR_FLOAT (arg2);
- if (FIXNUMP (arg1) /* common lisp spec */
+ 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 */
{ /* 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;
+ mpz_t x, *xp, r;
- x = XFIXNUM (arg1);
- y = XFIXNUM (arg2);
- acc = (y & 1 ? x : 1);
-
- while ((y >>= 1) != 0)
+ if (BIGNUMP (arg1))
+ xp = &XBIGNUM (arg1)->value;
+ else
{
- x *= x;
- if (y & 1)
- acc *= x;
+ mpz_init_set_si (x, XFIXNUM (arg1));
+ xp = &x;
}
- XSETINT (val, acc);
+
+ mpz_init (r);
+ mpz_pow_ui (r, *xp, XFIXNUM (arg2));
+
+ val = make_number (r);
+ mpz_clear (r);
+ if (xp == &x)
+ mpz_clear (x);
return val;
}
return make_float (pow (XFLOATINT (arg1), XFLOATINT (arg2)));
diff --git a/test/src/floatfns-tests.el b/test/src/floatfns-tests.el
index 7714c05d60..4fab032ecb 100644
--- a/test/src/floatfns-tests.el
+++ b/test/src/floatfns-tests.el
@@ -46,4 +46,8 @@
(should (= (+ (logb most-positive-fixnum) 1)
(logb (+ most-positive-fixnum 1)))))
+(ert-deftest bignum-expt ()
+ (should (= (expt 10 100)
+ (apply #'* (make-list 100 10)))))
+
(provide 'floatfns-tests)
next prev parent reply other threads:[~2018-08-12 16:34 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 [this message]
2018-08-13 12:21 ` Basil L. Contovounesios
2018-08-14 0:21 ` Andy Moreton
2018-08-15 23:41 ` Andy Moreton
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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