From a238800e34c1490e1581bbc923a5512dc61ffd11 Mon Sep 17 00:00:00 2001 From: "Vladimir V. Kisil" Date: Wed, 31 Jul 2013 16:44:18 +0100 Subject: [PATCH 6/9] Additional log evaluation rule. log(p^a) -> a*log(p) if p is positive and a is real. Signed-off-by: Vladimir V. Kisil --- check/exam_inifcns.cpp | 11 +++++++++++ ginac/inifcns_trans.cpp | 4 ++++ 2 files changed, 15 insertions(+) diff --git a/check/exam_inifcns.cpp b/check/exam_inifcns.cpp index 424aa26..2191172 100644 --- a/check/exam_inifcns.cpp +++ b/check/exam_inifcns.cpp @@ -295,6 +295,17 @@ static unsigned inifcns_consist_log() if (!e1.is_equal(e2)) ++result; + if (!ex(log(pow(p,a))).is_equal(a*log(p))) + ++result; + + // shall not do for non-real powers + if (ex(log(pow(p,z))).is_equal(z*log(p))) + ++result; + + // shall not do for non-positive basis + if (ex(log(pow(a,b))).is_equal(b*log(a))) + ++result; + return result; } diff --git a/ginac/inifcns_trans.cpp b/ginac/inifcns_trans.cpp index 0d4904a..4b5a1cd 100644 --- a/ginac/inifcns_trans.cpp +++ b/ginac/inifcns_trans.cpp @@ -173,6 +173,10 @@ static ex log_eval(const ex & x) if (t.info(info_flags::real)) return t; } + + // log(pow(a,b)) -> b*log(a) (if a>0 and b is real) + if (is_exactly_a(x) && x.op(0).info(info_flags::positive) && x.op(1).info(info_flags::real)) + return x.op(1)*log(x.op(0)); return log(x).hold(); } -- 1.8.4.rc3