choice_iterator.hpp

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