* Implementation of GiNaC's symbolic exponentiation (basis^exponent). */
/*
- * GiNaC Copyright (C) 1999-2006 Johannes Gutenberg University Mainz, Germany
+ * GiNaC Copyright (C) 1999-2007 Johannes Gutenberg University Mainz, Germany
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
case info_flags::algebraic:
return !exponent.info(info_flags::integer) ||
basis.info(inf);
+ case info_flags::expanded:
+ return (flags & status_flags::expanded);
}
return inherited::info(inf);
}
* - ^(0,c) -> 0 or exception (depending on the real part of c)
* - ^(1,x) -> 1
* - ^(c1,c2) -> *(c1^n,c1^(c2-n)) (so that 0<(c2-n)<1, try to evaluate roots, possibly in numerator and denominator of c1)
+ * - ^(^(x,c1),c2) -> ^(x,c1*c2) if x is positive and c1 is real.
* - ^(^(x,c1),c2) -> ^(x,c1*c2) (c2 integer or -1 < c1 <= 1, case c1=1 should not happen, see below!)
* - ^(*(x,y,z),c) -> *(x^c,y^c,z^c) (if c integer)
* - ^(*(x,c1),c2) -> ^(x,c2)*c1^c2 (c1>0)
if (is_exactly_a<function>(ebasis))
return ex_to<function>(ebasis).power(eexponent);
+ // Turn (x^c)^d into x^(c*d) in the case that x is positive and c is real.
+ if (is_exactly_a<power>(ebasis) && ebasis.op(0).info(info_flags::positive) && ebasis.op(1).info(info_flags::real))
+ return power(ebasis.op(0), ebasis.op(1) * eexponent);
+
if (exponent_is_numerical) {
// ^(c1,c2) -> c1^c2 (c1, c2 numeric(),
if (is_exactly_a<numeric>(sub_exponent)) {
const numeric & num_sub_exponent = ex_to<numeric>(sub_exponent);
GINAC_ASSERT(num_sub_exponent!=numeric(1));
- if (num_exponent->is_integer() || (abs(num_sub_exponent) - (*_num1_p)).is_negative())
+ if (num_exponent->is_integer() || (abs(num_sub_exponent) - (*_num1_p)).is_negative()) {
return power(sub_basis,num_sub_exponent.mul(*num_exponent));
+ }
}
}
if (num_exponent->is_integer() && is_exactly_a<mul>(ebasis)) {
return expand_mul(ex_to<mul>(ebasis), *num_exponent, 0);
}
-
+
+ // (2*x + 6*y)^(-4) -> 1/16*(x + 3*y)^(-4)
+ if (num_exponent->is_integer() && is_exactly_a<add>(ebasis)) {
+ const numeric icont = ebasis.integer_content();
+ const numeric& lead_coeff =
+ ex_to<numeric>(ex_to<add>(ebasis).seq.begin()->coeff).div_dyn(icont);
+
+ const bool canonicalizable = lead_coeff.is_integer();
+ const bool unit_normal = lead_coeff.is_pos_integer();
+
+ if (icont != *_num1_p) {
+ return (new mul(power(ebasis/icont, *num_exponent), power(icont, *num_exponent))
+ )->setflag(status_flags::dynallocated);
+ }
+
+ if (canonicalizable && (! unit_normal)) {
+ if (num_exponent->is_even()) {
+ return power(-ebasis, *num_exponent);
+ } else {
+ return (new mul(power(-ebasis, *num_exponent), *_num_1_p)
+ )->setflag(status_flags::dynallocated);
+ }
+ }
+ }
+
// ^(*(...,x;c1),c2) -> *(^(*(...,x;1),c2),c1^c2) (c1, c2 numeric(), c1>0)
// ^(*(...,x;c1),c2) -> *(^(*(...,x;-1),c2),(-c1)^c2) (c1, c2 numeric(), c1<0)
if (is_exactly_a<mul>(ebasis)) {
return (new add(sum))->setflag(status_flags::dynallocated | status_flags::expanded);
}
-/** Expand factors of m in m^n where m is a mul and n is and integer.
+/** Expand factors of m in m^n where m is a mul and n is an integer.
* @see power::expand */
ex power::expand_mul(const mul & m, const numeric & n, unsigned options, bool from_expand) const
{
epvector::const_iterator last = m.seq.end();
epvector::const_iterator cit = m.seq.begin();
while (cit!=last) {
- if (is_exactly_a<numeric>(cit->rest)) {
- distrseq.push_back(m.combine_pair_with_coeff_to_pair(*cit, n));
- } else {
- // it is safe not to call mul::combine_pair_with_coeff_to_pair()
- // since n is an integer
- numeric new_coeff = ex_to<numeric>(cit->coeff).mul(n);
- if (from_expand && is_exactly_a<add>(cit->rest) && new_coeff.is_pos_integer()) {
- // this happens when e.g. (a+b)^(1/2) gets squared and
- // the resulting product needs to be reexpanded
- need_reexpand = true;
- }
- distrseq.push_back(expair(cit->rest, new_coeff));
+ expair p = m.combine_pair_with_coeff_to_pair(*cit, n);
+ if (from_expand && is_exactly_a<add>(cit->rest) && ex_to<numeric>(p.coeff).is_pos_integer()) {
+ // this happens when e.g. (a+b)^(1/2) gets squared and
+ // the resulting product needs to be reexpanded
+ need_reexpand = true;
}
+ distrseq.push_back(p);
++cit;
}