term.hpp

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/*
MIT License
 
Copyright (c) 2025 [Peter Robinson]
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
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The above copyright notice and this permission notice shall be included in all
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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*/
 
#ifndef PL_SEARCH_TERM_HPP
#define PL_SEARCH_TERM_HPP
 
#include <iostream>
#include <string>
 
#include "typedefs.hpp"
 
namespace pl_search {
 
class Engine;
 
class Term : public std::enable_shared_from_this<Term> {
protected:
  virtual bool isEqualTo(Term &t) const = 0;
 
  virtual Term *deref_term() { return this; }
 
public:
  virtual TermPtr dereference() { return shared_from_this(); };
 
  virtual std::string repr() const { return "TERM"; }
 
  virtual bool isLessThan(Term &t) const = 0;
 
  virtual bool unifyWith(Engine *engine, TermPtr t) { return false; }
 
  virtual bool is_var() { return false; }
 
  Term() {}
 
  virtual ~Term() {} // Virtual destructor
 
  friend std::ostream &operator<<(std::ostream &os, const Term &t) {
    os << t.repr();
    return os;
  }
 
  friend bool operator<(Term &t1, Term &t2);
 
  friend bool operator<=(Term &t1, Term &t2);
 
  friend bool operator==(Term &t1, Term &t2);
};
 
} // namespace pl_search
 
#endif // PL_SEARCH_TERM_HPP