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Michael Hopkins
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 Posted: Fri Oct 28, 2005 1:28 pm Post subject: valarray subclass value assignment |
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Hi all
I have a subclass of valarray<T> thus
template <typename T>
class uo_val : public std::valarray<T>
{
public:
uo_val ( ) : std::valarray<T>() {}
uo_val (const int sz ) : std::valarray<T>( sz ) {}
uo_val (const int sz, const T fill ) : std::valarray<T>( fill, sz ) {}
//etc..
};
and I want to define an operator
uo_val& uo_val::operator=( const T & )
to assign all values to the supplied T using valarray's operator
valarray& valarray::operator=( const T & )
But neither (1) nor (2) below work and I'm not sure why.
uo_val& operator=( const T & val ) { // (1)
return std::valarray<T>::operator=( val );
}
Refuses to compile with:
error: invalid initialization of reference of type 'hr::uo_val<double>&'
from expression of type 'std::valarray<double>'
uo_val& operator=( const T & val ) { // (2)
*this = val;
return *this;
}
Compiles but gives runtime error signal 11 (SIGSEGV)
Could someone please enlighten me?
Many thanks - please CC to my email
Michael
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Rolf Magnus
Guest
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| Posted: Fri Oct 28, 2005 1:50 pm Post subject: Re: valarray subclass value assignment |
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Michael Hopkins wrote:
| Quote: | But neither (1) nor (2) below work and I'm not sure why.
uo_val& operator=( const T & val ) { // (1)
return std::valarray<T>::operator=( val );
}
Refuses to compile with:
error: invalid initialization of reference of type 'hr::uo_val<double>&'
from expression of type 'std::valarray<double>'
|
You can't bind a reference to uo_val to an std::valarray<T>.
| Quote: | uo_val& operator=( const T & val ) { // (2)
*this = val;
return *this;
}
Compiles but gives runtime error signal 11 (SIGSEGV)
|
Well, this is a recursion. Your operator= will call itself over and over
again, usually until your stack is exhausted.
How about:
uo_val& operator=( const T & val )
{
std::valarray<T>::operator=( val );
return *this;
}
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Kai-Uwe Bux
Guest
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| Posted: Fri Oct 28, 2005 1:52 pm Post subject: Re: valarray subclass value assignment |
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Michael Hopkins wrote:
| Quote: |
Hi all
I have a subclass of valarray<T> thus
template <typename T
class uo_val : public std::valarray
{
public:
uo_val ( ) : std::valarray
uo_val (const int sz ) : std::valarray<T>( sz ) {}
uo_val (const int sz, const T fill ) : std::valarray<T>( fill, sz ) {}
//etc..
};
and I want to define an operator
uo_val& uo_val::operator=( const T & )
to assign all values to the supplied T using valarray's operator
valarray& valarray::operator=( const T & )
But neither (1) nor (2) below work and I'm not sure why.
uo_val& operator=( const T & val ) { // (1)
return std::valarray<T>::operator=( val );
|
you are returning the subobject of type std::valarray<T>. Try:
uo_val & operator= ( T const & t ) {
std::valarray<T>::operator= ( t );
return( *this );
}
| Quote: | }
Refuses to compile with:
error: invalid initialization of reference of type 'hr::uo_val<double>&'
from expression of type 'std::valarray<double>'
uo_val& operator=( const T & val ) { // (2)
*this = val;
return *this;
}
Compiles but gives runtime error signal 11 (SIGSEGV)
|
You have an infinite loop. The segfault is most likely a stack overflow.
Best
Kai-Uwe Bux
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