142 lines
5.7 KiB
C++
142 lines
5.7 KiB
C++
// @HEADER
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// ***********************************************************************
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//
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// Teuchos: Common Tools Package
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// Copyright (2004) Sandia Corporation
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//
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// Under terms of Contract DE-AC04-94AL85000, there is a non-exclusive
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// license for use of this work by or on behalf of the U.S. Government.
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//
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// This library is free software; you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 2.1 of the
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// License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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// USA
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// Questions? Contact Michael A. Heroux (maherou@sandia.gov)
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//
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// ***********************************************************************
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// @HEADER
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#ifndef TEUCHOS_IMPLICIT_CAST_HPP
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#define TEUCHOS_IMPLICIT_CAST_HPP
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#include "Teuchos_ConfigDefs.hpp"
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namespace Teuchos {
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/** \brief Perform an implicit cast of concrete types with the casted object
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* returned by value.
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*
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* This function is used as:
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\code
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TypeTo myCast( const TypeFrom& a )
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{
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return Teuchos::implicit_cast<TypeTo>(a);
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}
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\endcode
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*
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* This function will only compile for types where an implicit conversion from
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* objects of type <tt>TypeFrom</tt> to type <tt>TypeTo</tt> exists. Note
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* that this is a weaker operation than a <tt>static_cast<TypeTo>(t)</tt> in
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* that the static cast will actually compile in cases where the implicit
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* conversion would not compile and may result in incorrect code. This
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* function can not result in incorrect code, assuming that the implicit
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* conversions themselves do no result in incorrect code (which is another
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* matter all together).
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*
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* This function is especially helpful when one needs to be careful of what
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* specific type is passed in as a formal argument to a function and in
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* comparing values. In particular, using this function is far safer than
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* using <tt>TypeTo(t)</tt> in cases where <tt>TypeTo</tt> is a built in type
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* since <tt>TypeTo(t)</tt> in these cases is equivalent to <tt>(TypeTo)t</tt>
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* which is an unchecked sledge-hammer cast of the worst kind.
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*
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* \ingroup teuchos_language_support_grp
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*/
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template<class TypeTo, class TypeFrom>
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inline TypeTo implicit_cast( const TypeFrom& t ) { return t; }
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/** \brief Perform an implicit cast of reference types with a reference being
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* returned.
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*
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* This function is used as:
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\code
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TypeTo& myPtrCast( TypeFrom &ref1 )
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{
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return Teuchos::implicit_ref_cast<TypeTo>(ref1);
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}
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\endcode
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* This function will only compile for types where an implicit conversion from
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* references of type <tt>TypeFrom&</tt> to references of <tt>TypeTo&</tt>
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* exists. It is allowed for the type <tt>TypeFrom</tt> and <tt>TypeTo</tt>
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* to actually be <tt>const</tt> types. For example, we can have <tt>TypeFrom
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* = const std::iostream</tt> and <tt>TypeTo = const std::ostream</tt> and
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* <tt>Teuchos::implicit_ref_cast<const
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* std::ostream>(Teuchos::getConst(std::cout))</tt> would compile just fine.
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* Note that this is a weaker operation than a
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* <tt>static_cast<TypeTo&>(t)</tt> in that the static cast will actually
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* compile in cases where the implicit conversion would not compile and may
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* result in incorrect code. For example, a static cast from a base to a
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* derived class will compile (and may be wrong) while this implicit cast
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* function will not compile for casts from base to derived classes. This
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* function can not result in incorrect code, assuming that the implicit
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* conversions themselves do no result in incorrect code (which is another
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* matter all together).
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*
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* \ingroup teuchos_language_support_grp
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*/
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template<class TypeTo, class TypeFrom>
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inline TypeTo& implicit_ref_cast( TypeFrom& t ) { return t; }
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/** \brief Perform an implicit cast of pointer types with a pointer being
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* returned.
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*
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* This function is used as:
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\code
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TypeTo* myPtrCast( TypeFrom *ptr1 )
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{
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return Teuchos::implicit_ptr_cast<TypeTo>(ptr1);
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}
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\endcode
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* This function will only compile for types where an implicit conversion from
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* pointers of type <tt>TypeFrom*</tt> to pointers of type <tt>TypeTo*</tt>
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* exists. It is allowed for the type <tt>TypeFrom</tt> and <tt>TypeTo</tt>
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* to actually be <tt>const</tt> types. For example, we can have <tt>TypeFrom
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* = const std::iostream</tt> and <tt>TypeTo = const std::ostream</tt> and
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* <tt>Teuchos::implicit_ptr_cast<const
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* std::ostream>(&Teuchos::getConst(std::cout))</tt> would compile just fine.
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*
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* Note that this is a weaker operation than a
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* <tt>static_cast<TypeTo*>(t)</tt> in that the static cast will actually
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* compile in cases where the implicit conversion would not compile and may
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* result in incorrect code. For example, a static cast up from a base class
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* to a derived class will compile (and may be wrong) while this implicit cast
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* function will not compile for such casts. This function can not result in
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* incorrect code, assuming that the implicit conversions themselves do no
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* result in incorrect code (which is another matter all together).
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*
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* \ingroup teuchos_language_support_grp
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*/
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template<class TypeTo, class TypeFrom>
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inline TypeTo* implicit_ptr_cast( TypeFrom* t ) { return t; }
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} // end namespace Teuchos
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#endif // TEUCHOS_IMPLICIT_CAST_HPP
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