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#ifndef moses_FeatureFunction_h
#define moses_FeatureFunction_h
#include <vector>
#include "ScoreProducer.h"
namespace Moses
{
class TargetPhrase;
class Hypothesis;
class ChartHypothesis;
class FFState;
class InputType;
class ScoreComponentCollection;
/** base class for all feature functions.
* @todo is this for pb & hiero too?
* @todo what's the diff between FeatureFunction and ScoreProducer?
*/
class FeatureFunction: public ScoreProducer
{
public:
virtual bool IsStateless() const = 0;
virtual ~FeatureFunction();
};
/** base class for all stateless feature functions.
* eg. phrase table, word penalty, phrase penalty
*/
class StatelessFeatureFunction: public FeatureFunction
{
public:
//! Evaluate for stateless feature functions. Implement this.
virtual void Evaluate(
const TargetPhrase& cur_hypo,
ScoreComponentCollection* accumulator) const;
// If true, this value is expected to be included in the
// ScoreBreakdown in the TranslationOption once it has been
// constructed.
// Default: true
virtual bool ComputeValueInTranslationOption() const;
bool IsStateless() const;
};
/** base class for all stateful feature functions.
* eg. LM, distortion penalty
*/
class StatefulFeatureFunction: public FeatureFunction
{
public:
/**
* \brief This interface should be implemented.
* Notes: When evaluating the value of this feature function, you should avoid
* calling hypo.GetPrevHypo(). If you need something from the "previous"
* hypothesis, you should store it in an FFState object which will be passed
* in as prev_state. If you don't do this, you will get in trouble.
*/
virtual FFState* Evaluate(
const Hypothesis& cur_hypo,
const FFState* prev_state,
ScoreComponentCollection* accumulator) const = 0;
virtual FFState* EvaluateChart(
const ChartHypothesis& /* cur_hypo */,
int /* featureID */,
ScoreComponentCollection* accumulator) const = 0;
//! return the state associated with the empty hypothesis for a given sentence
virtual const FFState* EmptyHypothesisState(const InputType &input) const = 0;
bool IsStateless() const;
};
}
#endif
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