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// -*- mode: C++; c-indent-level: 4; c-basic-offset: 4; indent-tabs-mode: nil; -*-
//
// Nullable.h: Rcpp R/C++ interface class library -- SEXP container which can be NULL
//
// Copyright (C) 2015 Dirk Eddelbuettel and Daniel C. Dillon
//
// This file is part of Rcpp.
//
// Rcpp is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 2 of the License, or
// (at your option) any later version.
//
// Rcpp is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Rcpp. If not, see <http://www.gnu.org/licenses/>.
#ifndef Rcpp_Nullable_h
#define Rcpp_Nullable_h
// We looked into the safe_bool_idiom [1] but found that more trouble than is
// warranted here. We first and foremost want an operator SEXP() which got in
// the way of redefining operator bool.
// [1] http://www.artima.com/cppsource/safebool.html)
namespace Rcpp {
template<class T>
class Nullable {
public:
/**
* Empty no-argument constructor of a Nullable object
*
* Assigns (R's) NULL value, and sets validator to FALSE
*/
inline Nullable() : m_sexp(R_NilValue), m_set(false) {}
/**
* Template constructor of a Nullable object
*
* Assigns object, and set validator to TRUE
*/
inline Nullable(const T &t) : m_sexp(t), m_set(true) {}
/**
* Standard constructor of a Nullable object
*
* @param SEXP is stored
*/
inline Nullable(SEXP t) {
m_sexp = t;
m_set = true;
}
public:
/**
* Copy constructor for Nullable object
*
* @param SEXP is used to update internal copy
*/
inline Nullable &operator=(SEXP sexp) {
m_sexp = sexp;
m_set = true;
return *this;
}
/**
* operator SEXP() to return nullable object
*
* @throw 'not initialized' if object has not been set
*/
inline operator SEXP() const {
checkIfSet();
return m_sexp;
}
/**
* get() accessor for object
*
* @throw 'not initialized' if object has not been set
*/
inline SEXP get() const {
checkIfSet();
return m_sexp;
}
/**
* Boolean test for usability as a T
*/
inline bool isUsable() const {
return m_set && !Rf_isNull(m_sexp);
}
/**
* Boolean test for NULL
*
* @throw 'not initialized' if object has not been set
*/
inline bool isNull() const {
checkIfSet();
return Rf_isNull(m_sexp);
}
/**
* Boolean test for not NULL
*
* @throw 'not initialized' if object has not been set
*/
inline bool isNotNull() const {
return ! isNull();
}
/**
* Test function to check if object has been initialized
*
*/
inline bool isSet(void) const { return m_set; }
/**
* Returns m_sexp as a T
*/
inline T as() { return get(); }
/**
* Return a clone of m_sexp as a T
*/
inline T clone() const { return Rcpp::clone(get()); }
private:
SEXP m_sexp;
bool m_set;
inline void checkIfSet(void) const {
if (!m_set) {
throw ::Rcpp::exception("Not initialized");
}
}
};
}
#endif
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