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2023-01-11Record left-linear expansion and forest formatJSDurand
Now the grammar will record the left-linear expansions when generating the nondeterministic finite automaton frmo its rules, and will record whether an edge in the nondeterministic finite automaton comes from a left-linear expansion. The latter is needed because while performing a chain-rule derivation, we do not need the left-linear expanded derivations in the "first layer". This might well have been the root cause of the bad performance of the previous version of this package. Also I have figured out how to properly generate and handle parse forests while manipulating the "chain-rule machine".
2023-01-06Save before system restart.JSDurand
I am about to re-start my system, so I save before any crashes happen.
2023-01-05singly labelled graphsJSDurand
Now I have a new type of labelled graphs, which can index vertices by labels, but not index edges by labels. The biggest difference is that I do not have to keep a hashmap of edge targets by labels, and I do not have to guard against the duplication of nodes with the same set of edges. I guard against nodes with the same label, though. Also, in this graph, both vertices and edges have one label at a time, whereas in the previous labelled graph there can be a multitude of edges between the same source and target nodes, but with different labels. Now it remains to test this type of graphs, and to think through how we attach forest fragments to nondeterministic finite automata edges, and how to join forest fragments together while skipping nullable edges, in order to finish the "compilation" part.
2023-01-03structural change: separate crates outJSDurand
I put functionalities that are not strictly core to separate crates, so that the whole package becomes more modular, and makes it easier to try other parsing algorithms in the future. Also I have to figure the forests out before finishing the core chain-rule algorithm, as the part about forests affects the labels of the grammars directly. From my experiences in writing the previous version, it is asking for trouble to change the labels type dramatically at a later point: too many places need to be changed. Thus I decide to figure the rough part of forests out. Actually I only have to figure out how to attach forests fragments to edges of the underlying atomic languages, and the more complex parts of putting forests together can be left to the recorders, which is my vision of assembling semi-ring values during the chain-rule machine. It should be relatively easy to produce forests fragments from grammars since we are just trying to extract some information from the grammar, not to manipulate those information in some complicated way. We have to do some manipulations in the process, though, in order to make sure that the nulling and epsilon-removal processes do not invalidate these fragments.
2022-12-23renaming core to chain and some other changesJSDurand
Some changes: - The core crate is renamed to "chain". - The crate "viz" is added, which will provide layered graph drawing algorithms. - A function is added to convert from a grammar to the regular language of its left-linear closures. - A function is added to convert from a nondeterministic finite automaton to its "null" closure. A null closure is the same automaton with edges added, as if some edges are "null". Whether an edge is null is determined by a function. Combined with the previous change, we can convert a grammar to the regular language of the null closure of its left-linear closures. --- Now it remains to test more grammars and add an Atom trait, before finishing the part about compilations.