| /* interpolation/integ_eval_macro.h |
| * |
| * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or (at |
| * your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, but |
| * WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| */ |
| |
| /* function for doing the spline integral evaluation |
| which is common to both the cspline and akima methods |
| */ |
| |
| static inline double |
| integ_eval (double ai, double bi, double ci, double di, double xi, double a, |
| double b) |
| { |
| const double r1 = a - xi; |
| const double r2 = b - xi; |
| const double r12 = r1 + r2; |
| const double bterm = 0.5 * bi * r12; |
| const double cterm = (1.0 / 3.0) * ci * (r1 * r1 + r2 * r2 + r1 * r2); |
| const double dterm = 0.25 * di * r12 * (r1 * r1 + r2 * r2); |
| |
| return (b - a) * (ai + bterm + cterm + dterm); |
| } |
