====== Atomic Parameters ======

This tutorial describes the current procedure for adding a parameter to an Atom. This is used when an Atom needs to use its bits for some kind of information.

===== Declare Compilation Constants =====

First, we need to describe in the Element how big of a field we want to use, and where to place it inside the atom. We need to use the bits on the right hand part of the atom first, since a number of ones on the left hand side are already used. For instance, let's declare a small field which can hold a byte:

<code>
enum
{
    BITS = P::BITS_PER_ATOM,
    
    BYTE_BITS_LENGTH = 8,
    BYTE_BITS_POSITION = BITS - BYTE_BITS_LENGTH - 1
};
</code>

These constants are then used to describe a BitField, like so:

<code>
typedef BitField<BitVector<BITS>, BYTE_BITS_LENGTH, BYTE_BITS_POSITION> AFByteBits;
</code>

make sure that BitField is included in the file by adding:

<code>
#include "BitField.h"
</code>

to the top of the file.

===== Make Getter and Setter =====

We now need methods which access these bits. In the public section of your elemenet, place:

<code>
u32 GetByteBits(const T& us) const
{
    return AFByteBits::Read(this->GetBits(us));
}

void SetByteBits(T& us, u32 bits) const
{
    AFByteBits::Write(this->GetBits(us), bits & 0xff);
}
</code>

Now we are able to Get and Set these bits.

===== Set Default Value =====

We should also set some sort of default value for these bits. This is done by overriding the **GetDefaultAtom()** method. Place in the public section of your element:

<code>

static const u32 TYPE()
{
    return THE_INSTANCE.GetType();
}

virtual const T& GetDefaultAtom() const
{
    static T defaultAtom(TYPE(), 0, 0, 0);
    this->SetByteBits(defaultAtom, 0 /* Or other default value */);
    
    return defaultAtom;
}
</code>

In this example, the default atom has its bitfield set to 0. We can use this call during the behavior method as well to read or write bits of other atoms.