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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*/
 
#ifndef PL_SEARCH_TERM_HPP
#define PL_SEARCH_TERM_HPP
 
#include <iostream>
#include <string>
 
#include "typedefs.hpp"
 
namespace pl_search {
 
  class Trail;
 
  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(Trail* trail, 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);
  };
 
  bool unify(TermPtr t1, TermPtr t2, Trail* trail);
 
} // namespace pl_search
 
#endif // PL_SEARCH_TERM_HPP