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In the file automaton_test.py there is a test (test_transition_lt) that's a bit strange, feels like there's been a copy-paste from the one above

Shouldn't it be something like

def test_transition_lt(self):
        self.assetTrue(t1.__lt__(t2))

where t1 and t2 are previously defined transitions?

Regards,
Manuele

Evaluate if it will be convenient to add the said method.

Nell' handout 5 nella cella 6 viene invocato all_terminals ma esce questo errore. Ho provato a invocarlo pure nel playground ma non va lo stesso.

It could be reasonable to allow for the prod argument of Grammar.step and Grammar.{left, right}most to be not only a production index, but also a Production. This will avoid the need for G.P.index(prod) in calling code.

Such class can provide several functionalities now spread out in the library (using dicts, or dods):

• a read access where missing index(es) lead to less code (no try or if),
• a write access with conflict check to avoid multiple entries per index(es),
• a pretty print (based on current dict2table and dod2table).

Such class could simplify the LL/LR lectures quite a bit.

In order to simplify the presentation of algorithms exploring the computation graph of (N)PDAs it could be convenient to have an immutable version of such data structures.

If you restrict a grammar using the restrict_to method and you don't pass the start symbol within the symbols to keep, what happens to the grammar? Should the method throw some sort of error/exception? Should it try to retrieve the first (single) lhs of another kept production rule in order to get a new start symbol, if possible?

If you define an object of the AnnotatedTreeWalker class that makes use of attributes within the registered functions, saving the ATW object with the save method does not save the attributes used, as in the case of the following example:

from liblet import AnnotatedTreeWalker, Tree

tree = Tree({'name': 'test'})

test_atw = AnnotatedTreeWalker('name')
@test_atw.register
def test(visit, ast):
    test_atw.VAR = 5
    print(test_atw.VAR)
    print(3)

test_atw(tree) # out: 5 3

test_atw.save('test.atw')
test_atw = AnnotatedTreeWalker.load('test.atw')

test_atw(tree) # out: exception

By running the above code, an error is raised:

NameError: name 'test_atw' is not defined

The Stack data structure should iterate from the top (via sequence of pop), currently it iterates in the reverse order:

list(Stack([1,2,3]))

should produce [3, 2, 1] but now produces [1, 2, 3].

This will break compatibility quite badly. At least the https://github.com/let-unimi/handouts should be revised in accordance to the change.