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/*
Copyright (C) 2021 Fredrik Johansson
This file is part of Calcium.
Calcium is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "fexpr.h"
/*
Sets *res* to an expression for the multivariate polynomial *poly*
using the expressions in *vars* as variables. If *vars* is *NULL*,
the symbols *x1*, *x2*, ..., *xn* are used.
*/
void
fexpr_set_fmpz_mpoly(fexpr_t res, const fmpz_mpoly_t poly, const fexpr_vec_t vars, const fmpz_mpoly_ctx_t ctx)
{
slong len, nvars, i, j, factors_len;
fexpr_ptr terms;
fexpr_ptr factors;
fexpr_t op, t;
ulong * exp;
nvars = ctx->minfo->nvars;
len = poly->length;
if (len == 0)
{
fexpr_zero(res);
return;
}
if (fmpz_mpoly_is_fmpz(poly, ctx))
{
fexpr_set_fmpz(res, poly->coeffs);
return;
}
if (vars == NULL)
{
fexpr_vec_t v;
fexpr_vec_init(v, nvars);
/* FIXME */
for (i = 0; i < nvars; i++)
{
fexpr_vec_entry(v, i)->data[0] = FEXPR_TYPE_SMALL_SYMBOL | ('x' << 8) | (('1' + i) << 16);
}
fexpr_set_fmpz_mpoly(res, poly, v, ctx);
fexpr_vec_clear(v);
return;
}
exp = flint_malloc(sizeof(ulong) * nvars);
len = poly->length;
fexpr_init(t);
fexpr_init(op);
factors = _fexpr_vec_init(nvars + 1);
/* todo: just allocate one array */
terms = _fexpr_vec_init(len);
fexpr_set_symbol_str(op, "Mul");
for (i = 0; i < len; i++)
{
int constant_term;
fmpz_mpoly_get_term_exp_ui(exp, poly, i, ctx);
factors_len = 0;
constant_term = (i == len - 1);
for (j = 0; constant_term && j < nvars; j++)
if (exp[j] != 0)
constant_term = 0;
if (!fmpz_is_one(poly->coeffs + i) || constant_term)
{
fexpr_set_fmpz(factors, poly->coeffs + i);
factors_len = 1;
}
for (j = 0; j < nvars; j++)
{
if (exp[j] != 0)
{
if (exp[j] == 1)
{
fexpr_set(factors + factors_len, fexpr_vec_entry(vars, j));
}
else
{
fexpr_set_ui(t, exp[j]);
fexpr_pow(factors + factors_len, fexpr_vec_entry(vars, j), t);
}
factors_len++;
}
}
if (factors_len == 1)
fexpr_set(terms + i, factors);
else
{
fexpr_call_vec(terms + i, op, factors, factors_len);
}
}
if (len == 1)
{
fexpr_swap(res, terms);
}
else
{
fexpr_set_symbol_str(op, "Add");
fexpr_call_vec(res, op, terms, len);
}
flint_free(exp);
_fexpr_vec_clear(factors, nvars + 1);
_fexpr_vec_clear(terms, len);
fexpr_clear(op);
fexpr_clear(t);
}
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