choice_iterator.hpp

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/*
MIT License
 
...license text...
 
*/
 
#ifndef PL_SEARCH_CHOICE_ITERATOR_HPP
#define PL_SEARCH_CHOICE_ITERATOR_HPP
 
#include "engine.hpp"
#include "typedefs.hpp"
 
#include <vector>
 
namespace pl_search {
class Engine;
class PVar;
 
class ChoiceIterator {
public:
  virtual bool has_next() = 0;
 
  virtual bool make_choice() = 0;
 
  virtual bool test_choice() { return true; }
 
  virtual ~ChoiceIterator() = default;
};
 
class VarChoiceIterator : public ChoiceIterator {
public:
  VarChoiceIterator(Engine *engine, PVarPtr v, std::vector<TermPtr> ch)
      : engine(engine), var(v), choices(ch), index(0) {}
 
  bool has_next() override { return index < choices.size(); }
 
  virtual bool make_choice() override {
    TermPtr t = choices[index++];
    return engine->unify(var, t)  && test_choice();
  }
 
protected:
  Engine *engine;               
  int index;                    
  PVarPtr var;                  
  std::vector<TermPtr> choices; 
};
 
} // namespace pl_search
 
#endif // PL_SEARCH_CHOICE_ITERATOR_HPP