noalias.hpp

来自「boost库提供标准的C++ API 配合dev c++使用,功能更加强大」· HPP 代码 · 共 103 行

//
//  Copyright (c) 2003
//  Michael Stevens
//
//  Permission to use, copy, modify, distribute and sell this software
//  and its documentation for any purpose is hereby granted without fee,
//  provided that the above copyright notice appear in all copies and
//  that both that copyright notice and this permission notice appear
//  in supporting documentation.  The authors make no representations
//  about the suitability of this software for any purpose.
//  It is provided "as is" without express or implied warranty.
//

#ifndef BOOST_UBLAS_NOALIAS_H
#define BOOST_UBLAS_NOALIAS_H

namespace boost { namespace numeric { namespace ublas {

    // Assignment proxy.
    // Provides temporary free assigment when LHS has no alias on RHS
    template<class C>
    class noalias_proxy:
        private boost::nonassignable {
    public:
        typedef typename C::closure_type closure_type;

        BOOST_UBLAS_INLINE
        noalias_proxy (C& lval):
            boost::nonassignable (), lval_ (lval) {}
        BOOST_UBLAS_INLINE
        noalias_proxy (const noalias_proxy& p):
            boost::nonassignable (), lval_ (p.lval_) {}

        template <class E>
        BOOST_UBLAS_INLINE
        closure_type &operator= (const E& e) {
            lval_.assign (e);
            return lval_;
        }

        template <class E>
        BOOST_UBLAS_INLINE
        closure_type &operator+= (const E& e) {
            lval_.plus_assign (e);
            return lval_;
        }

        template <class E>
        BOOST_UBLAS_INLINE
        closure_type &operator-= (const E& e) {
            lval_.minus_assign (e);
            return lval_;
        }

    private:
        closure_type lval_;
    };

    // Improve syntax of effcient assignment where no aliases of LHS appear on the RHS
    //  noalias(lhs) = rhs_expression
    template <class C>
    BOOST_UBLAS_INLINE
    noalias_proxy<C> noalias (C& lvalue) {
        return noalias_proxy<C> (lvalue);
    }
    template <class C>
    BOOST_UBLAS_INLINE
    noalias_proxy<const C> noalias (const C& lvalue) {
        return noalias_proxy<const C> (lvalue);
    }

}}}

#endif