Vector properties - GNU Scientific Library -- Reference Manual

The following functions are defined for real and complex vectors. For complex vectors both the real and imaginary parts must satisfy the conditions.

— Function: int gsl_vector_isnull (const gsl_vector * v)
— Function: int gsl_vector_ispos (const gsl_vector * v)
— Function: int gsl_vector_isneg (const gsl_vector * v)
— Function: int gsl_vector_isnonneg (const gsl_vector * v)

These functions return 1 if all the elements of the vector v are zero, strictly positive, strictly negative, or non-negative respectively, and 0 otherwise.

8.3.10 Vector properties