Array size

[Luc Claustres]

Is it possible to retrieve the number
of elements in a template array
dynamically allocated ?

void allocate()
{
int size = ...
T *pointer = new T[size];
}

void compute(T *pointer)
{
// Here I need the size but I can only access the pointer
}

Thanks.

 

[David Harmon]

On Sun, 5 Dec 2004 22:06:35 +0100 in comp.lang.c++, "Luc Claustres"

Is it possible to retrieve the number
of elements in a template array
dynamically allocated ?

void allocate()
{
int size = ...
T *pointer = new T[size];
}

void compute(T *pointer)
{
// Here I need the size but I can only access the pointer
}

Use std::vector, then use the vector's size() member function to get
the size. Avoid roll-your-own substitutes for standard library
classes.

 

[Buster]

Is it possible to retrieve the number
of elements in a template array
dynamically allocated ?

In general no. Store the size too if you're going to need it.

void allocate()
{
int size = ...
T *pointer = new T[size];

Memory leak.

}

void compute(T *pointer)
{
// Here I need the size but I can only access the pointer

In fact you can't access either.

 

[Virtual]

Not really, but you could add another template parameter that comes
before anything that's deduced by the compiler. I've assumed function
templates for simplicity.

template<class T>
void allocate()
{
int size = T *pointer = new T[size];
compute<size>(T);
}

template<int U, class T>
void compute(T *pointer)
{
//do whatever you want here
}

Hope that helps.

 

[David Harmon]

On 6 Dec 2004 02:43:34 -0800 in comp.lang.c++, "Virtual"

template<class T>
void allocate()
{
int size = T *pointer = new T[size];
Bogus.

compute<size>(T);

Also bogus, using a variable size for a template parameter.