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namespace zypp
{
/** \page CodePitfalls Code Pitfalls - Frequently made mistakes
\section TriBoolCompare Comparing TriBool values
Comparing two \ref TriBool values is not as easy as it might look like,
because the \c TriBool::operator== and \c TriBool::operator!= return
a \ref TriBool.
For example is <tt>(indeterminate==indeterminate)</tt> not \c true, but
\c indeterminate. That's why the following snippet does not do what the
author expected:
\code
// buggy option class
struct Option
{
public:
Option()
: _value( indeterminate )
{}
bool get() const
{ return ( _value == indeterminate ) ? true : bool(_value); }
void set( bool new_r )
{ _value = new_r; }
private:
tribool _value;
};
\endcode
You find that \c get() returns \c false as long as the option is unset,
and not \c true as the code suggests. That's because <tt>(_value==indeterminate)</tt>
returns \c indeterminate.
\note Always use \c indeterminate(_value) to test whether a TriBools value is \c indeterminate:
\code
bool get() const
{ return indeterminate( _value ) ? true : bool(_value); }
\endcode
\code
tribool _value;
...
if ( indeterminate( _value ) )
{ ... } // indeterminate
else if ( _value )
{ ... } // true
else
{ ... } // false
\endcode
<HR>
*/
}
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