Changing data within bytes...

Lisp: where you have to modify the language to get anything useful done.

I don't really get what's going on here. You made a macro/function that lets you take the nth element of any sequence? Doesn't sound that special to me. :-\

Changing bits isn't hard if you write a function for it. In C++:

 Spoiler

Code:

template<typename type>
void setbit(type& variable, size_t bit, bool on)
{
    unsigned char * bytePtr = (unsigned char *) (&variable);
    size_t byteOffset = bit / 8;
    bytePtr += byteOffset;
    size_t bitOffset = bit % 8;

    if(on)
    {
        *bytePtr = *bytePtr | ( (unsigned char) (1) << (7 - bitOffset));
    }
    else
    {
        *bytePtr = *bytePtr & ( ( ~((unsigned char) (1)) ) << (7 - bitOffset));
    }
}

template<typename type>
bool getbit(const type& variable, size_t bit)
{
    const unsigned char * bytePtr = (const unsigned char *) (&variable);
    size_t byteOffset = bit / 8;
    bytePtr += byteOffset;
    size_t bitOffset = bit % 8;

    unsigned char byteCopy = *bytePtr;
    byteCopy = byteCopy | ( (unsigned char) (1) << (7 - bitOffset)); // Set the bit in a copy of the byte to 1, then check if the setting of the bit changed the byte
    if(byteCopy == *bytePtr)
    {
        return true;
    }
    else
    {
        return false;
    }
}

Edit: I wrote that code a while ago. A non-template function taking a void* would result in smaller code.