declare array of objects in header file

[Philipp]

Hello, I've got a class Lattice which is declared like that:

// file: lattice.h

class Lattice:public EventChooser{
public:
Lattice(Lattice Parameters* params);
virtual ~Lattice();
// (...snip...)

private:
// How do I declare this member array in the lattice.h file?
// The following doesn't seem to work
LatticeSite** lattice; // does not compile
};


// file: lattice.cpp

Lattice::Lattic e(LatticeParame ters* params){

// Initializing 3D lattice
LatticeSite lattice[Ni][Nj][Nk];

for(int i=0; i<Ni; i++)
for(int j=0; j<Nj; j++)
for(int k=0; k<Nk; k++)
lattice[i][j][k].setValues(i,j, k,0);
}

The class LatticeSite has a default constructor.
So I don't know how to declare "lattice" which is an array of LatticeSite
objects in the file lattice.h.

Any ideas? Thanks Phil

[Allan Bruce]

Re: declare array of objects in header file


"Philipp" <_NO_S~P~A~M_ki tschen@hotmail. com> wrote in message
news:3f8ebb67$1 @epflnews.epfl. ch...[color=blue]
>
> Hello, I've got a class Lattice which is declared like that:
>
> // file: lattice.h
>
> class Lattice:public EventChooser{
> public:
> Lattice(Lattice Parameters* params);
> virtual ~Lattice();
> // (...snip...)
>
> private:
> // How do I declare this member array in the lattice.h file?
> // The following doesn't seem to work
> LatticeSite** lattice; // does not compile
> };[/color]

Is LatticeSite declared in this header file? If not then remember to
#include it
BTW LatticeSite** is not setting an array, this is a pointer to a pointer to
a LatticeSite object. An array would be declared like
LatticeSite lattice[10];
However, if you dont know how many elements are required at compile time
then you will have to use a pointer and then initialise it using new, e.g.

LatticeSite *lattice; // declared in class definition

LatticeSite = new lattice[x]; // declared elsewhere (i suggest
LatticeSite::in it)

HTH
Allan

[Howard]

Re: declare array of objects in header file


">[color=blue]
> LatticeSite = new lattice[x]; // declared elsewhere (i suggest
> LatticeSite::in it)
>[/color]

I take it you mean:

lattice = new LatticeSite[x]; ?


And I have no idea what you mean by suggesting he "declare" it in a
(static?) init function...? (Are you referring to 'x' being assigned a
value elsewhere?)


-Howard

[Philipp]

Re: declare array of objects in header file

Hmm
I guess i can't allocate a static array with a variable as size.

int N=2;
int a[N];

won't work. Ok I'll to do do it dynamically then :-)

[Allan Bruce]

Re: declare array of objects in header file


"Howard" <alicebt@hotmai l.com> wrote in message
news:bmmfpg$nrs @dispatch.conce ntric.net...[color=blue]
>
> ">[color=green]
> > LatticeSite = new lattice[x]; // declared elsewhere (i suggest
> > LatticeSite::in it)
> >[/color]
>
> I take it you mean:
>
> lattice = new LatticeSite[x]; ?[/color]

Yes I do - need some sleep!
[color=blue]
>
>
> And I have no idea what you mean by suggesting he "declare" it in a
> (static?) init function...? (Are you referring to 'x' being assigned a
> value elsewhere?)
>[/color]

I meant x was declared somewhere so that the memory is allocated
dynamically, but even better:

// Lattice.h
#include "LatticeSit e.h"

class Lattice:public EventChooser
{
public:
bool Init(int xiNumElements);
....
private:
LatticeSite* mLattice;
};

//Lattice.cpp
bool Lattice::Init(i nt xiNumElements)
{
if ( (mLattice = new LatticeSite[xiNumElements]) == NULL)
return true; // couldnt allocate the memory

return false; // no problems :o)
}

I hope thats clear
Allan

[Ron Natalie]

Re: declare array of objects in header file


"Philipp" <_NO_S~P~A~M_ki tschen@hotmail. com> wrote in message news:3f8ec2ed$1 @epflnews.epfl. ch...[color=blue]
> Hmm
> I guess i can't allocate a static array with a variable as size.
>
> int N=2;
> int a[N];
>[/color]
You can't declare an array anywhere with a given size that is not a constant expression.

vector<int> a(N);

would probably work fine for you.