// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2023 Google Inc. All rights reserved.
// http://ceres-solver.org/
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#ifndef CERES_PUBLIC_FIRST_ORDER_FUNCTION_H_
#define CERES_PUBLIC_FIRST_ORDER_FUNCTION_H_

#include "ceres/internal/export.h"

namespace ceres {

// A FirstOrderFunction object implements the evaluation of a function
// and its gradient.
class CERES_EXPORT FirstOrderFunction {
 public:
  virtual ~FirstOrderFunction();

  // cost is never null. gradient may be null. The return value
  // indicates whether the evaluation was successful or not.
  virtual bool Evaluate(const double* const parameters,
                        double* cost,
                        double* gradient) const = 0;
  virtual int NumParameters() const = 0;
};

}  // namespace ceres

#endif  // CERES_PUBLIC_FIRST_ORDER_FUNCTION_H_
