Re: gnucap-0.32

On Wednesday 18 December 2002 12:57 pm, xhecs wrote:
> what does this line do?
>
> CARD_LIST::putbefore =
>               CARD_LIST::fat_iterator(&(CARD_LIST::card_list),
>                                   CARD_LIST::card_list.end())


CARD_LIST::putbefore keeps track of where things are being added.

It is a static member of CARD_LIST, because most circuits have more 
than one CARD_LIST.  Gnucap does not flatten circuits like Spice does.

Think of it as a pointer to where to add the next component.

In C++, an "iterator" is like a smart pointer.  You treat it like a 
pointer.  It actually behaves the way you would like pointers to 
behave.  It is used to iterate over a container.

In C, you can use a pointer to traverse an array.  This is familiar to 
all C programmers.  In C++, iterators let you traverse linked lists (or 
any container) in the same way, with identical syntax.

A "fat_iterator" (in Gnucap) is an extended form of an iterator, that 
also contains information on which container it belongs to.



CARD_LIST::card_list is the root list for storing the circuit.  Think 
of it as a many-branched tree, where the nodes of the tree are lists.




CARD_LIST::fat_iterator is a class.  Using a class name like a function 
call means it is being used as a constructor.  In this case, it 
constructs a fat_iterator pointing to the end of the root list, then 
assigns it to CARD_LIST::putbefore.


So, in one line ....

That line of code sets the insert point, so when you add components 
they are added to the end of the root circuit.


al.