Here is the updated patch.
thanks
Ramakrishnan
From e320d79c8f3cd8b7ddcb9c2d13356e34a3346cfe Mon Sep 17 00:00:00 2001
From: Ramakrishnan Muthukrishnan <[email protected]>
Date: Sun, 31 Oct 2010 23:22:52 +0530
Subject: [PATCH] Fix for bug #31464. expt needs to treat negative bases specially.
* libguile/numbers.c: If base is negative, expt needs to find
-x^n = (-1^n) * (|x|^n). We find x^n and then if n is odd, we
also multiply the result with -1. These changes apply only for
cases where n is an integer.
* test-suite/tests/numbers.test: Two new test cases for expt. For
cases where the base is negative and the power to be raised is
not an integer, the result should be a complex number.
---
libguile/numbers.c | 13 ++++++++++++-
test-suite/tests/numbers.test | 15 ++++++++++++++-
2 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/libguile/numbers.c b/libguile/numbers.c
index fbc6cc8..4b81d98 100644
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -5445,12 +5445,23 @@ SCM_DEFINE (scm_expt, "expt", 2, 0, 0,
"Return @var{x} raised to the power of @var{y}.")
#define FUNC_NAME s_scm_expt
{
- if (scm_is_true (scm_exact_p (x)) && scm_is_integer (y))
+ if (scm_is_true (scm_exact_p (y)) && scm_is_integer (y))
return scm_integer_expt (x, y);
else if (scm_is_real (x) && scm_is_real (y) && scm_to_double (x) >= 0.0)
{
return scm_from_double (pow (scm_to_double (x), scm_to_double (y)));
}
+ else if (scm_is_real (x) && scm_is_integer (y) && (scm_to_double (x) < 0))
+ {
+ double result;
+
+ result = pow (-scm_to_double (x), scm_to_double (y));
+
+ if (scm_is_true (scm_odd_p (y)))
+ return scm_from_double (-result);
+ else
+ return scm_from_double (result);
+ }
else
return scm_exp (scm_product (scm_log (x), y));
}
diff --git a/test-suite/tests/numbers.test b/test-suite/tests/numbers.test
index 3c3e14f..637449f 100644
--- a/test-suite/tests/numbers.test
+++ b/test-suite/tests/numbers.test
@@ -2892,7 +2892,20 @@
(pass-if "(= 1 (expt 0 0))" (= 1 (expt 0 0)))
(pass-if "(= 1 (expt 0 0.0))" (= 1 (expt 0 0.0)))
(pass-if "(= 1 (expt 0.0 0))" (= 1 (expt 0.0 0)))
- (pass-if "(= 1 (expt 0.0 0.0))" (= 1 (expt 0.0 0.0))))
+ (pass-if "(= 1 (expt 0.0 0.0))" (= 1 (expt 0.0 0.0)))
+ ;; tests for non zero values of base and exponent.
+ (pass-if "(eqv-loosely? -2742638075.5 (expt -2742638075.5 1))"
+ (eqv-loosely? -2742638075.5 (expt -2742638075.5 1)))
+ (pass-if "(eqv-loosely? 4.0 (expt -2.0 2.0))"
+ (eqv-loosely? 4.0 (expt -2.0 2.0)))
+ (pass-if "(eqv-loosely? -0.125 (expt -2.0 -3.0))"
+ (eqv-loosely? -0.125 (expt -2.0 -3.0)))
+ (pass-if "(eqv-loosely? -0.125 (expt -2 -3.0))"
+ (eqv-loosely? -0.125 (expt -2 -3.0)))
+ (pass-if "(eqv-loosely? 0.25 (expt 2.0 -2.0))"
+ (eqv-loosely? 0.25 (expt 2.0 -2.0)))
+ (pass-if "(eqv-loosely? 1.0000000000000002+1.7320508075688772i (expt -8 1/3))"
+ (eqv-loosely? 1.0000000000000002+1.7320508075688772i (expt -8 1/3))))
;;;
;;; asinh
--
1.7.2.3
