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#ifndef __ALG_UMINDIR_H_
#define __ALG_UMINDIR_H_

#include "space.hh"
#include "functional.hh"
#include "lnsrch.hh"

namespace RVLUmin {

  using RVL::Vector;
  using RVL::FunctionalEvaluation;
  using RVLAlg::Terminator;

  /** Abstract interface for computation of search 
      directions, in support of line search methods.
      Since computation can succeed or fail, must have 
      character of terminator.
  */

  template<typename Scalar>
  class UMinDir: public Terminator {
  public:
    UMinDir() {}
    UMinDir(UMinDir<Scalar> const &) {}
    virtual ~UMinDir() {}

    // note that Terminator::query must be defined by instantiable subclass 
    /** Returns search direction in mutable first argument */
    virtual void calcDir(Vector<Scalar> & dir,
			 FunctionalEvaluation<Scalar> & fx) = 0;
    /** Use data generated during line search to update any internals */
    virtual void updateDir(LineSearchAlg<Scalar> const & ls) = 0;
    /** Reinitialize direction computation */
    virtual void resetDir() = 0;
    /** verbose output stream */
    
    virtual ostream & write(ostream & str) const = 0;
  };
}

#endif