double pythag ( double a, double b );
double r8_abs ( double x );
double r8_max ( double x, double y );
double r8_min ( double x, double y );
double r8_sign ( double x );
int rs ( int n, double a[], double w[], double z[] );
int tql2 ( int n, double d[], double e[], double z[] );
void tred2 ( int n, double a[], double d[], double e[], double z[] );

