From e320d79c8f3cd8b7ddcb9c2d13356e34a3346cfe Mon Sep 17 00:00:00 2001 From: Ramakrishnan Muthukrishnan 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