root/library/bdm/math/functions.h @ 620

//
// C++ Interface: itpp_ext
//
// Description:
//
//
// Author: smidl <smidl@utia.cas.cz>, (C) 2008
//
// Copyright: See COPYING file that comes with this distribution
//
//
#ifndef FN_H
#define FN_H

#include "../bdmerror.h"
#include "../base/bdmbase.h"

namespace bdm {

//! class representing function \f$f(x) = a\f$, here \c rv is empty
class constfn : public fnc {
        //! value of the function
        vec val;

public:
        //vec eval() {return val;};
        //! inherited
        vec eval ( const vec &cond ) {
                return val;
        };
        //!Default constructor
        constfn ( const vec &val0 ) : fnc(), val ( val0 ) {
                dimy = val.length();
        };
};

//! Class representing function \f$f(x) = Ax+B\f$
class linfn: public fnc {
        //! Identification of \f$x\f$
        RV rv;
        //! Matrix A
        mat A;
        //! vector B
        vec B;
public :
        vec eval ( const vec &cond ) {
                bdm_assert_debug ( cond.length() == A.cols(), "linfn::eval Wrong cond." );
                return A * cond + B;
        }

//              linfn evalsome ( ivec &rvind );
        //!default constructor
        linfn ( ) : fnc(), A ( ), B () { };
        //! Set values of \c A and \c B
        void set_parameters ( const mat &A0 , const vec &B0 ) {
                A = A0;
                B = B0;
                dimy = A.rows();
        };
};


/*!
\brief Class representing a differentiable function of two variables \f$f(x,u)\f$.

Function of two variables.

TODO:
1) Technically, it could have a common parent (e.g. \c fnc ) with other functions. For now, we keep it as it is.
2) It could be generalized into multivariate form, (which was original meaning of \c fnc ).
*/
class diffbifn: public fnc {
protected:
        //! Indentifier of the first rv.
        RV rvx;
        //! Indentifier of the second rv.
        RV rvu;
        //! cache for rvx.count()
        int dimx;
        //! cache for rvu.count()
        int dimu;
public:
        //! Evaluates \f$f(x0,u0)\f$ (VS: Do we really need common eval? )
        vec eval ( const vec &cond ) {
                bdm_assert_debug ( cond.length() == ( dimx + dimu ), "linfn::eval Wrong cond." );
                return eval ( cond ( 0, dimx - 1 ), cond ( dimx, dimx + dimu - 1 ) );//-1 = end (in matlab)
        }

        //! Evaluates \f$f(x0,u0)\f$
        virtual vec eval ( const vec &x0, const vec &u0 ) {
                return zeros ( dimy );
        };
        //! Evaluates \f$A=\frac{d}{dx}f(x,u)|_{x0,u0}\f$ and writes result into \c A . @param full denotes that even unchanged entries are to be rewritten. When, false only the changed elements are computed. @param x0 numeric value of \f$x\f$, @param u0 numeric value of \f$u\f$ @param A a place where the result will be stored.
        virtual void dfdx_cond ( const vec &x0, const vec &u0, mat &A , bool full = true ) {};
        //! Evaluates \f$A=\frac{d}{du}f(x,u)|_{x0,u0}\f$ and writes result into \c A . @param full denotes that even unchanged entries are to be rewritten. When, false only the changed elements are computed.        @param x0 numeric value of \f$x\f$, @param u0 numeric value of \f$u\f$ @param A a place where the result will be stored.
        virtual void dfdu_cond ( const vec &x0, const vec &u0, mat &A, bool full = true ) {};
        //!Default constructor (dimy is not set!)
        diffbifn () : fnc() {};
        //! access function
        int _dimx() const {
                return dimx;
        }
        //! access function
        int _dimu() const {
                return dimu;
        }
};

//! Class representing function \f$f(x,u) = Ax+Bu\f$
//TODO can be generalized into multilinear form!
class bilinfn: public diffbifn {
        mat A;
        mat B;
public :
        //!\name Constructors
        //!@{

        bilinfn () : diffbifn (), A(), B() { }

        bilinfn ( const mat &A0, const mat &B0 ) {
                set_parameters ( A0, B0 );
        }

        //! Alternative initialization
        void set_parameters ( const mat &A0, const mat &B0 ) {
                bdm_assert ( A0.rows() == B0.rows(), "bilinfn matrices must have the same number of rows" );
                A = A0;
                B = B0;
                dimy = A.rows();
                dimx = A.cols();
                dimu = B.cols();
        }
        //!@}

        //!\name Mathematical operations
        //!@{
        inline vec eval ( const  vec &x0, const vec &u0 ) {
                bdm_assert_debug ( x0.length() == dimx, "bilinfn::eval Wrong xcond." );
                bdm_assert_debug ( u0.length() == dimu, "bilinfn::eval Wrong ucond." );
                return A*x0 + B*u0;
        }

        void dfdx_cond ( const vec &x0, const vec &u0, mat &F, bool full ) {
                bdm_assert_debug ( ( F.cols() == A.cols() ) && ( F.rows() == A.rows() ), "Allocated F is not compatible." );
                if ( full ) F = A;      //else : nothing has changed no need to regenerate
        }

        void dfdu_cond ( const vec &x0, const vec &u0, mat &F,  bool full = true ) {
                bdm_assert_debug ( ( F.cols() == B.cols() ) && ( F.rows() == B.rows() ), "Allocated F is not compatible." );
                if ( full ) F = B;      //else : nothing has changed no need to regenerate
        }
        //!@}
};

} //namespace
#endif // FN_H