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/*
Copyright (C) 2020 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 "ca.h"
int
ca_ext_can_evaluate_qqbar(const ca_ext_t x, ca_ctx_t ctx)
{
if (CA_EXT_IS_QQBAR(x))
return 1;
if (CA_EXT_HEAD(x) == CA_Sqrt ||
CA_EXT_HEAD(x) == CA_Sign ||
CA_EXT_HEAD(x) == CA_Abs ||
CA_EXT_HEAD(x) == CA_Re ||
CA_EXT_HEAD(x) == CA_Im ||
CA_EXT_HEAD(x) == CA_Conjugate ||
CA_EXT_HEAD(x) == CA_Floor ||
CA_EXT_HEAD(x) == CA_Ceil)
return ca_can_evaluate_qqbar(CA_EXT_FUNC_ARGS(x), ctx);
if (CA_EXT_HEAD(x) == CA_Pow)
return ca_can_evaluate_qqbar(CA_EXT_FUNC_ARGS(x), ctx) &&
CA_IS_QQ(CA_EXT_FUNC_ARGS(x) + 1, ctx);
return 0;
}
int
ca_can_evaluate_qqbar(const ca_t x, ca_ctx_t ctx)
{
if (CA_IS_SPECIAL(x))
{
return 0;
}
else if (CA_IS_QQ(x, ctx))
{
return 1;
}
else if (CA_FIELD_IS_NF(CA_FIELD(x, ctx)))
{
return 1;
}
else
{
slong nvars, i;
int res;
int * used;
nvars = CA_FIELD_LENGTH(CA_FIELD(x, ctx));
used = flint_calloc(nvars, sizeof(int));
fmpz_mpoly_q_used_vars(used, CA_MPOLY_Q(x), CA_FIELD_MCTX(CA_FIELD(x, ctx), ctx));
res = 1;
/* todo: exclude extension numbers that are not actually used */
for (i = 0; i < nvars; i++)
{
if (used[i])
{
if (!ca_ext_can_evaluate_qqbar(CA_FIELD_EXT_ELEM(CA_FIELD(x, ctx), i), ctx))
{
res = 0;
break;
}
}
}
flint_free(used);
return res;
}
}
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