Created
May 4, 2014 18:42
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#include <type_traits> | |
template< class ConditionType > | |
class Not | |
{ | |
ConditionType m_condition; | |
public: | |
using this_type = Not<ConditionType>; | |
template< class ...Args > | |
Not( Args&&... args ) | |
: m_condition( std::forward<Args>(args)... ) {} | |
Not( const Not& ) = default; | |
Not& operator=( const Not& ) = default; | |
template< class ...Args > | |
bool operator()( Args&&... args ) const | |
{ | |
return ! m_condition( std::forward<Args>(args)... ); | |
} | |
friend inline bool operator==( const Not& left, const Not& right ) | |
{ | |
return left.m_condition == right.m_condition; | |
} | |
friend inline bool operator<( const Not& left, const Not& right ) | |
{ | |
return left.m_condition < right.m_condition; | |
} | |
}; | |
class ConditionThatCompile | |
{ | |
int m_key; | |
public: | |
ConditionThatCompile( int key ) : m_key( key ) {} | |
bool operator()( const int& value ) const | |
{ | |
return m_key > value; | |
} | |
friend inline bool operator==( const ConditionThatCompile& left, const ConditionThatCompile& right ) | |
{ | |
return left.m_key == right.m_key; | |
} | |
friend inline bool operator<( const ConditionThatCompile& left, const ConditionThatCompile& right ) | |
{ | |
return left.m_key < right.m_key; | |
} | |
}; | |
class ConditionThatDoNotCompile | |
{ | |
public: | |
bool operator()( const int& value ) const | |
{ | |
return true; | |
} | |
friend inline bool operator==( const ConditionThatDoNotCompile& left, const ConditionThatDoNotCompile& right ) | |
{ | |
return true; | |
} | |
friend inline bool operator<( const ConditionThatDoNotCompile& left, const ConditionThatDoNotCompile& right ) | |
{ | |
return false; | |
} | |
}; | |
void do_something(); | |
void somewhere() | |
{ | |
Not<ConditionThatCompile> compiling_condition { 42 }; | |
auto other = compiling_condition; // error C2664: 'ConditionThatCompile::ConditionThatCompile(const ConditionThatCompile &)' : cannot convert argument 1 from 'Not<ConditionThatCompile>' to 'int' | |
if( compiling_condition( 100 ) ) | |
do_something(); | |
//Not<ConditionThatDoNotCompile> not_compiling_condition; | |
}; |
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