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/* overlap.c - when do two intervals overlap? */

#include <sys/types.h>
#include <euclid/clump.h>

/*
 * overlap() returns info on whether two intervals overlap.
 *
 * If min_overlap is +n, then the intervals must overlap by n
 * grid positions.
 * If min_overlap is 0, the intervals 'overlap' if their corners 
 * touch diagonally.
 * If min_overlap is -n, the intervals are considered to
 * overlap if there is a gap of n grid positions or less between them.
 *
 * If interval1 is before interval2 including min overlap
 * 	return -1
 *
 * If interval1 and interval2 overlap including min overlap
 * 	return  0
 *
 * If interval1 is after interval2 including min overlap
 * 	return  1
 */

int EG_overlap(Interval *interval1_ptr, Interval *interval2_ptr, int min_overlap)
{

  int delta = 1 - min_overlap;

  if (interval1_ptr->begin < interval2_ptr->begin)
    {
      if (interval1_ptr->end < interval2_ptr->begin - delta)
	return(-1);
      else
	return(0);
    }
  else
    {
      if (interval2_ptr->end < interval1_ptr->begin - delta)
	return(1);
      else
	return(0);
    }

}