Geografic-Information-System/lib/vector/diglib/inside.c

/*
 ****************************************************************************
 *
 * MODULE:       Vector library 
 *              
 * AUTHOR(S):    Original author CERL, probably Dave Gerdes.
 *               Update to GRASS 5.7 Radim Blazek.
 *
 * PURPOSE:      Lower level functions for reading/writing/manipulating vectors.
 *
 * COPYRIGHT:    (C) 2001 by the GRASS Development Team
 *
 *               This program is free software under the GNU General Public
 *              License (>=v2). Read the file COPYING that comes with GRASS
 *              for details.
 *
 *****************************************************************************/
#include <grass/vector.h>

double
dig_x_intersect(double beg_x,
		double end_x, double beg_y, double end_y, double Y)
{
    double b, a;

    b = (end_x - beg_x) / (end_y - beg_y);
    a = beg_x - b * beg_y;
    return (a + b * Y);
}