From 9f410a18b08213185a6ae473295c9945ebdd9985 Mon Sep 17 00:00:00 2001 From: Richard Kreckel Date: Sat, 17 Nov 2001 18:48:46 +0000 Subject: [PATCH] * sqrfree(ex, lst): after factoring in the first variable, we forgot to call sqrfree again in the remaining variables for the constant term. For example, the expanded polynomial (x+1)*(y-1)*z only found one of the factors, no matter which variable order was specified in lst. --- ginac/normal.cpp | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-) diff --git a/ginac/normal.cpp b/ginac/normal.cpp index 4e2feb39..ee278681 100644 --- a/ginac/normal.cpp +++ b/ginac/normal.cpp @@ -1742,11 +1742,11 @@ static exvector sqrfree_yun(const ex &a, const symbol &x) * * @param a multivariate polynomial over Q[X] * @param x lst of variables to factor in, may be left empty for autodetection - * @return polynomail a in square-free factored form. */ + * @return polynomial a in square-free factored form. */ ex sqrfree(const ex &a, const lst &l) { - if (is_ex_of_type(a,numeric) || // algorithm does not trap a==0 - is_ex_of_type(a,symbol)) // shortcut + if (is_a(a) || // algorithm does not trap a==0 + is_a(a)) // shortcut return a; // If no lst of variables to factorize in was specified we have to @@ -1768,11 +1768,11 @@ ex sqrfree(const ex &a, const lst &l) // Find the symbol to factor in at this stage if (!is_ex_of_type(args.op(0), symbol)) throw (std::runtime_error("sqrfree(): invalid factorization variable")); - const symbol x = ex_to(args.op(0)); + const symbol &x = ex_to(args.op(0)); // convert the argument from something in Q[X] to something in Z[X] - numeric lcm = lcm_of_coefficients_denominators(a); - ex tmp = multiply_lcm(a,lcm); + const numeric lcm = lcm_of_coefficients_denominators(a); + const ex tmp = multiply_lcm(a,lcm); // find the factors exvector factors = sqrfree_yun(tmp,x); @@ -1781,10 +1781,10 @@ ex sqrfree(const ex &a, const lst &l) lst newargs = args; newargs.remove_first(); - // recurse down the factors in remaining vars + // recurse down the factors in remaining variables if (newargs.nops()>0) { - exvector::iterator i = factors.begin(), end = factors.end(); - while (i != end) { + exvector::iterator i = factors.begin(); + while (i != factors.end()) { *i = sqrfree(*i, newargs); ++i; } @@ -1796,10 +1796,16 @@ ex sqrfree(const ex &a, const lst &l) for (int p = 1; it!=itend; ++it, ++p) result *= power(*it, p); - // Yun's algorithm does not account for constant factors. (For - // univariate polynomials it works only in the monic case.) We can - // correct this by inserting what has been lost back into the result: - result = result * quo(tmp, result, x); + // Yun's algorithm does not account for constant factors. (For univariate + // polynomials it works only in the monic case.) We can correct this by + // inserting what has been lost back into the result. For completeness + // we'll also have to recurse down that factor in the remaining variables. + if (newargs.nops()>0) + result *= sqrfree(quo(tmp, result, x), newargs); + else + result *= quo(tmp, result, x); + + // Put in the reational overall factor again and return return result * lcm.inverse(); } -- 2.35.3