bool is_rref ( int m, int n, double *A );
double r8_epsilon ( );
void rref_compute ( int m, int n, double *A, double *A_RREF, int *a_cols );
double rref_determinant ( int n, double *A );
double *rref_inverse ( int n, double *A );
int rref_rank ( int m, int n, double *A );
double *rref_solve ( int m, int n, double *A, int nb, double *b );