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#ifndef __EST_FEATUREFUNCTIONCONTEXT_H__
#define __EST_FEATUREFUNCTIONCONTEXT_H__

/** A feature function context is the interface through which feature
  * functions are looked up. It is basicly a list of feature function
  * packages.
  * 
  * @author Richard Caley <rjc@cstr.ed.ac.uk>
  * @version $Id: EST_FeatureFunctionContext.h,v 1.2 2001/04/04 13:11:27 awb Exp $ */

#include "ling_class/EST_FeatureFunctionPackage.h"

class ling_class_init;

class EST_FeatureFunctionContext {
private:
  EST_TList <EST_FeatureFunctionPackage *> packages;
  EST_TStringHash <EST_Item_featfunc> cache;

protected:
  static EST_FeatureFunctionContext *global;

  void add_package(EST_FeatureFunctionPackage *package);
  EST_FeatureFunctionPackage *get_package(const EST_String name) const;

  EST_String get_featfunc_name(const EST_Item_featfunc func, int &found) const;

public:
  static const EST_String separator;

  EST_FeatureFunctionContext(void);
  ~EST_FeatureFunctionContext(void);

  void clear_cache(void);
  void add_package(const EST_String name);
  bool package_included(const EST_String name) const;
  const EST_Item_featfunc get_featfunc(const EST_String name, 
				 int must=0);
  const EST_Item_featfunc get_featfunc(const EST_String package,
				 const EST_String name, 
				 int must=0);

protected:
  static void class_init(void);

  friend class ling_class_init;

  friend void EST_register_feature_function_package(const char *name, void (*init_fn)(EST_FeatureFunctionPackage &p));
  friend void register_featfunc(const EST_String &name, const EST_Item_featfunc func);
  friend const EST_Item_featfunc get_featfunc(const EST_String &name,int must);
  friend EST_String get_featname(const EST_Item_featfunc func);
};

#endif

