Creating Linked Lists in Python

[grocery_stocker]

On Mar 21, 8:47 am, grocery_stocker <cdal... at gmail.com> wrote:
> On Mar 21, 6:38 am, Tim Chase <python.l... at tim.thechases.com> wrote:
>
>
>
> > > For example, this means that there can be a start node supposedly.
> > > Having a value of 0. It is pointing to node 1 with the value of "a"
> > > and to node 2 with the value of "b". Trying to make something like an
> > > NFA. Where id be changing regular expressions to NFAs.
>
> > John has already pointed out the preconception problems of
> > "linked list".
>
> > In the past, I've done NFA with a state machine:
>
> >    (STATE_A,
> >     STATE_B,
> >     STATE_C,
> >     STATE_D,
> >     ) = range(4)
>
> >    transitions = {
> >      # values are tuples of (newstate, transition_function)
> >      STATE_A: [
> >        (STATE_B, lambda x: x > 5),
> >        (STATE_C, lambda x: x > 10),
> >        (STATE_D, lambda x: x > 100),
> >        ],
> >      STATE_B: [
> >        (STATE_A, lambda x: x < 5),
> >        (STATE_C, lambda x: x > 10),
> >        ],
> >      STATE_C: [
> >        (STATE_B, lambda x: x < 10),
> >        (STATE_D, lambda x: x > 100),
> >        ],
> >      STATE_D: [],
> >      }
>
> > You may have to carry around extra information regarding your
> > state, and tweak accordingly.  Instead of tuples of (newstate,
> > transition_function), you could just use transition functions
> > that return the new state, or None if they're not satisfied.
>
> > You then simply maintain your current state, and then test your
> > incoming stream of tokens/data against your transition function
> > to see if you can transition to the resulting state.  Depending
> > on whether you need back-tracking, you'll want to gather all the
> > possible results, or otherwise may just settle for the first
> > available transition to a new state.
>
> And if you don't mind me asking. How do you invoke lambda from
> transitions?


Disregard that. I think I figured it out.

If you had something like...

>>> transitions = {1: [2, lambda x: 2*x]}

You would probably call it like...

>>> transitions[1][1](4)
8