Re: gtransall: recursive variant of gtrans

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Sat, Jan 10, 2026 at 07:57:52AM +0800, 管理员 wrote:
> static GEN _gtransall_wrap(void *E, GEN x) {
> 	(void)E; return gtransall(x);
> }
> 
> GEN gtransall(GEN x) {
> 	long i, j, l, lc, t = typ(x);
> 	GEN L, res;
> 
> 	l = lg(x);
> 	switch (t) {
> 	case t_VEC: t = t_COL; break;
> 	case t_COL: t = t_VEC; break;
> 	case t_MAT:
> 		if (l < 2) return cgetg(1,t_MAT);
> 		lc = lgcols(x);
> 		res = cgetg(lc, t_MAT);
> 		for (i = 1; i < lc; i++) {
> 			GEN y = cgetg(l, t_COL);
> 			for (j = 1; j < l; j++) gel(y,j) = gtransall(gcoeff(x,i,j));
> 			gel(res,i) = y;
> 		}
> 		return res;
> 	case t_LIST:
> 		return genapply(NULL, _gtransall_wrap, x);
> 	default:
> 		/* t_CLOSURE uses t_VEC for internal, convert to t_COL is invalid */
> 		if (is_noncalc_t(t) || !is_recursive_t(t)) return gcopy(x);
> 	}
> 
> 	res = cgetg(l, t);
> 	i = lontyp[t];
> 	memcpy(res + 1, x + 1, (i - 1)*sizeof(long));
> 	while (i < l) {
> 		gel(res,i) = gtransall(gel(x,i));
> 		i++;
> 	}
> 	return res;
> }

Thanks! Could you explain whath this fonction does, why this is needed and give
some example ?

Also, you should use cgetg_copy, instead of memcpy.

Cheers,
Bill