1 /*
2 Copyright (C) 2019 Daniel Schultz
3
4 This file is part of FLINT.
5
6 FLINT is free software: you can redistribute it and/or modify it under
7 the terms of the GNU Lesser General Public License (LGPL) as published
8 by the Free Software Foundation; either version 2.1 of the License, or
9 (at your option) any later version. See <https://www.gnu.org/licenses/>.
10 */
11
12 #include "fq_nmod_mpoly.h"
13
fq_nmod_mpoly_sub_fq_nmod(fq_nmod_mpoly_t A,const fq_nmod_mpoly_t B,const fq_nmod_t c,const fq_nmod_mpoly_ctx_t ctx)14 void fq_nmod_mpoly_sub_fq_nmod(
15 fq_nmod_mpoly_t A,
16 const fq_nmod_mpoly_t B,
17 const fq_nmod_t c,
18 const fq_nmod_mpoly_ctx_t ctx)
19 {
20 slong d = fq_nmod_ctx_degree(ctx->fqctx);
21 slong N = mpoly_words_per_exp(B->bits, ctx->minfo);
22 slong Blen = B->length;
23
24 fq_nmod_mpoly_assert_canonical(B, ctx);
25
26 if (fq_nmod_is_zero(c, ctx->fqctx))
27 {
28 fq_nmod_mpoly_set(A, B, ctx);
29 return;
30 }
31
32 if (Blen < 1)
33 {
34 fq_nmod_mpoly_set_fq_nmod(A, c, ctx);
35 fq_nmod_mpoly_neg(A, A, ctx);
36 return;
37 }
38
39 if (mpoly_monomial_is_zero(B->exps + (Blen - 1)*N, N))
40 {
41 if (A != B)
42 {
43 fq_nmod_mpoly_fit_length_reset_bits(A, Blen, B->bits, ctx);
44 _nmod_vec_set(A->coeffs, B->coeffs, d*(Blen - 1));
45 mpoly_copy_monomials(A->exps, B->exps, Blen, N);
46 _fq_nmod_mpoly_set_length(A, Blen, ctx);
47 }
48
49 n_fq_sub_fq_nmod(A->coeffs + d*(Blen - 1), B->coeffs + d*(Blen - 1), c, ctx->fqctx);
50 if (_n_fq_is_zero(A->coeffs + d*(Blen - 1), d))
51 _fq_nmod_mpoly_set_length(A, Blen - 1, ctx);
52 }
53 else
54 {
55 if (A != B)
56 {
57 fq_nmod_mpoly_fit_length_reset_bits(A, Blen + 1, B->bits, ctx);
58 _nmod_vec_set(A->coeffs, B->coeffs, d*Blen);
59 mpoly_copy_monomials(A->exps, B->exps, Blen, N);
60 }
61 else
62 {
63 fq_nmod_mpoly_fit_length(A, Blen + 1, ctx);
64 }
65
66 mpoly_monomial_zero(A->exps + N*Blen, N);
67 n_fq_set_fq_nmod(A->coeffs + d*Blen, c, ctx->fqctx);
68 _n_fq_neg(A->coeffs + d*Blen, A->coeffs + d*Blen, d, fq_nmod_ctx_mod(ctx->fqctx));
69 _fq_nmod_mpoly_set_length(A, Blen + 1, ctx);
70 }
71 }
72