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/*
Copyright (C) 2022 Fredrik Johansson
This file is part of FLINT.
FLINT 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 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "gr_poly.h"
/* todo: overloadable function */
int
_gr_poly_derivative(gr_ptr res, gr_srcptr poly, slong len, gr_ctx_t ctx)
{
gr_method_binary_op_ui mul_ui = GR_BINARY_OP_UI(ctx, MUL_UI);
slong i;
slong sz = ctx->sizeof_elem;
int status = GR_SUCCESS;
for (i = 1; i < len; i++)
status |= mul_ui(GR_ENTRY(res, i - 1, sz), GR_ENTRY(poly, i, sz), i, ctx);
return status;
}
int
gr_poly_derivative(gr_poly_t res, const gr_poly_t poly, gr_ctx_t ctx)
{
int status;
slong len = poly->length;
if (len <= 1)
{
status = gr_poly_zero(res, ctx);
}
else
{
gr_poly_fit_length(res, len - 1, ctx);
status = _gr_poly_derivative(res->coeffs, poly->coeffs, len, ctx);
_gr_poly_set_length(res, len - 1, ctx);
/* todo: only call in nonzero characteristic */
_gr_poly_normalise(res, ctx);
}
return status;
}