This function is the interface to the reference class NLFC for
creating nonlinear constraints.
nlfc(G, h)List with elements: conType, G and h.
Object of class "matrix": A \((m \times n)\) matrix
containing the coefficients of the lefthand-side linear inequality
constraints.
Object of class NLFV: A \((m \times 1)\) vector
containing the coefficients of the righthand-side linear inequality
constraints as slot u.