valarray subclass value assignment

[Michael Hopkins]

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]

Michael Hopkins wrote:

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>.
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;
}

[Kai-Uwe Bux]

Michael Hopkins wrote:

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 );
you are returning the subobject of type std::valarray<T>. Try:

uo_val & operator= ( T const & t ) {
std::valarray<T>::operator= ( t );
return( *this );
}

}

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