clist.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_CLIST_HPP
#define PL_SEARCH_CLIST_HPP
 
#include "term.hpp"
#include "typedefs.hpp"
 
#include <list>
#include <sstream>
#include <string>
 
// CList objects replace Prolog lists for efficiency
// WARNING: Because the internal list is mutable care must be taken when using
// CList objects. For example, it might be necessary to copy the list before
// passing it to a function that might modify it or when binding a variable to
// a CList object.
// If a Prolog-like list is required, a user-defined class that implements the
// Term interface should be used (for example ConsList).
 
namespace pl_search {
 
class CList : public Term {
protected:
  std::list<TermPtr> &elements; 
 
public:
  CList(std::list<TermPtr> &elems) : elements(elems) {}
 
  std::string repr() const override {
    std::ostringstream oss;
    oss << "[";
    for (auto it = elements.begin(); it != elements.end(); ++it) {
      if (it != elements.begin()) {
        oss << ", ";
      }
      oss << (*it)->repr();
    }
    oss << "]";
    return oss.str();
  }
 
  bool isEqualTo(Term &other) const override {
    if (CList *list = dynamic_cast<CList *>(&other)) {
      return elements == list->elements;
    }
    return false;
  }
 
  bool isLessThan(Term &other) const override;
 
  void addElement(TermPtr element) { elements.push_back(element); }
 
  const std::list<TermPtr> &getElements() const { return elements; }
};
 
} // namespace pl_search
 
#endif // PL_SEARCH_CLIST_HPP