DefaultValue.h

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// # DefaultValue.h: fill a variable with its default value.
// # Copyright (C) 1995,1996,2000
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library 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 Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
// #                        520 Edgemont Road
// #                        Charlottesville, VA 22903-2475 USA
 
#ifndef CASA_DEFAULTVALUE_H
#define CASA_DEFAULTVALUE_H
 
#include <casacore/casa/aips.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// <summary>
// A templated function which sets a variable to a default value.
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="syang" date="1996/03/14" tests="tDefaultValue.cc" demos="">
// </reviewed>
 
// <prerequisite>
// </prerequisite>
//
// <etymology>
// The DefaultValue function name is derived from its use to fill a data type
// with a default value, usually zero.
// </etymology>
//
// <synopsis>
// The DefaultValue function is passed an instance of a data type and the
// variable is filled with a default value.  The majority of classes may
// use the templated version here.  Special classes may use their own
// non-templated specializations as demonstrated in
// ../Utilities/test/tDefaultValue.cc.
// </synopsis>
//
// <example>
// <srcblock>
// Int foo = 35;
// defaultValue(foo);
// AlwaysAssert(foo == 0, AipsError);
// Array<Float> bar;
// defaultValue(bar);
// AlwaysAssert(allEQ(bar, 0.0f), AipsError);
// </srcblock>
// A special class may need its own implementation:
// <srcblock>
// void defaultValue(MySpecialClass &val){
//  // make a default value be all zeros
//  val.operator()(IPosition(2,3,4)) = Table.keywords().defaultval();
// };
// </srcblock>
// </example>
//
// <motivation>
// We needed a common way of setting all objects to zero or some
// null/default value.  Specializing a templated function seemed the only way
// to reach everyone.
// </motivation>
//
// <templating arg=T>
//    <li> constructor T(Int)
//    <li> assignment operator (copy semantics)
// </templating>
//
// <thrown>
//    <li> none
// </thrown>
//
// <todo asof="1996/02/22">
//   <li> none
// </todo>
 
// <group name=defval>
 
template <class T>
inline void defaultValue(T &theValue) {
  theValue = T(0);
}
 
// </group>
 
}  // namespace casacore
 
#endif