/* interpolation/bsearch.h * * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2004 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 3 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. */ /* Author: G. Jungman */ #ifndef __GSL_INTERP_BSEARCH_H__ #define __GSL_INTERP_BSEARCH_H__ /* Perform a binary search of an array of values. * * The parameters index_lo and index_hi provide an initial bracket, * and it is assumed that index_lo < index_hi. The resulting index * is guaranteed to be strictly less than index_hi and greater than * or equal to index_lo, so that the implicit bracket [index, index+1] * always corresponds to a region within the implicit value range of * the value array. * * Note that this means the relationship of 'x' to x_array[index] * and x_array[index+1] depends on the result region, i.e. the * behaviour at the boundaries may not correspond to what you * expect. We have the following complete specification of the * behaviour. * Suppose the input is x_array[] = { x0, x1, ..., xN } * if ( x == x0 ) then index == 0 * if ( x > x0 && x <= x1 ) then index == 0, and sim. for other interior pts * if ( x == xN ) then index == N-1 * if ( x > xN ) then index == N-1 * if ( x < x0 ) then index == 0 */ size_t gsl_interp_bsearch( const double x_array[], double x, size_t index_lo, size_t index_hi ); #ifdef HAVE_INLINE extern inline size_t gsl_interp_bsearch( const double x_array[], double x, size_t index_lo, size_t index_hi ) { size_t ilo = index_lo; size_t ihi = index_hi; while(ihi > ilo + 1) { size_t i = (ihi + ilo)/2; if(x_array[i] > x) ihi = i; else ilo = i; } return ilo; } #endif /* HAVE_INLINE */ #endif /* __GSL_INTERP_BSEARCH_H__ */

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