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4 - Migrate Demo.java -> MetaGrammar.java
5 - Figure out serialization
7 - Clean up the prioritized-match garbage
8 - evil problems with (x y? z /ws)
11 - better ambiguity debugging tools / visualization
12 - ParseFailed, GSS, Walk, Parser, Sequence, Forest
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19 - finalize metagrammar and rdp-op's
24 - RFC2822 (email message/headers)
25 - clean up the whole Walk situation (?)
27 - what if Tree<> could unwrap itself?
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33 - serialization of parse tables
35 - "ambiguity modulo dropped fragments"?
36 - can this be checked statically?
37 - eliminated statically?
39 - substring parsing for better error messages
41 - right now I can only lift the last child in a forest... begs
42 the question of what the right representation for Forests is
43 if we need to be able to do lift operations on it.
46 - "Regular Right Part" grammars (NP Chapman, etc)
47 - Attribute unification
49 - inference of rejections for literals
50 - "prefer whitespace higher up" (?)
52 - Labeled edges on trees (associate a label with each slot in the
53 child array in Forest.Body? might make equality tough) --
54 equivalent to Feature Structures. Colon-labeling.
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59 - Partly-Linear-PATR? (O(n^6) unification grammar)
61 - Implement a k-token peek buffer (for each state, see if it "dead
62 ends" during the next k Phases based solely on state -- ignoring
65 - Arrange for the SPPF corresponding to dropped subtrees to never be
66 generated (or merged, etc)
68 - Is there any way we can avoid creating a GSS.Node instance for
69 nodes which are transient in the sense that they have only one
72 - Re-read Rekers, particularly the stuff on optimal sharing
74 - Isolate the Element objects from Parse.Table/GSS so we can move
77 - consider allowing a Forest.Body to represent some other Tree whose
78 Body's should be [recursively] considered part of this Forest.
80 - perhaps not: right now we have a nice situation where
81 Forest.Ref instances become immutable once iterator()ed. This
82 also gives us a strong place to to culling with the certainty
83 that we won't throw out a Body which would later be salvaged
84 by some yet-to-be-added dependency.
86 - Figure out if there is a way to:
88 - allow unwrapping of children other than the very last one.
90 - fold repetitions into an array form in Forest, before
91 conversion to Tree. The major problem here is that multiple
92 tree-arrays are possible, all of different lengths. Worse,
93 even if they're all the same length, not all elements belong
94 in the same "possibility vector" as all others. You
95 essentially need a GSS to represent the array, which perhaps
96 is what the unfolded form was in the first place.
98 - Wikipedia grammar (needs to be both lexerless and boolean)
101 => Ordered Choice (";" operator)
103 - bring back in parse-table phase resolution of precedence (just
104 like associativity). This can be inferred from the use of ">"
105 when the rules are in one of these special forms:
116 where "_" is anything and "E" is the defining nonterminal.
117 Essentially what we're looking for is the situation where the
118 leftmost portion of one rule produces another rule, and the
119 rightmost portion of the latter produces the former.
121 I'm not 100% certain that this is as "strong" as the prefer/avoid
122 form (try to prove this, you probably can), but it's "what people
123 intend" most of the time.
125 - implement Johnstone's algorithm for "reduced, resolved LR
126 tables" to eliminate superfluous reductions on
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132 - Rekers & Koorn note that GLR Substring Parsing can be used to do
133 really elegant and generalized "autocompletion".
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139 - Incremental parse table construction
140 - "lazy GLR" and "lazy trees" -> language with first-class CF matching
141 - perhaps linear boolean grammars instead? (linear time, quad space)
142 - Forest parsing => chained parsers
143 - unification parsing, attributes, etc
145 - Take another stab at maximal-match? Nonterminal not-followed-by is
147 - Error recovery based on substring parsing