#include <grass/gis.h>

double 
length (register int np, register double *x, register double *y)
{
  register double len;
  register int i;

  len = 0.0;
  for (i=0; i < (np-1); i++) 
     len += G_distance(*(x+i), *(y+i), *(x+i+1), *(y+i+1));

  return(len);
}