unikernel/duniverse/ocaml-re/TODO.txt

@@ -0,0 +1,81 @@
+* To compile r{i,j} we need a sequence that does not match epsilon
+  (or a constructor around an expression telling that this expression
+  does not match epsilon)
+* A subexpression repeated by an asterisk ( '*' ) or an interval
+  expression shall not match a null expression unless this is the only
+  match for the repetition or it is necessary to satisfy the exact or
+  minimum number of occurrences for the interval expression.
+* There might be a typo in deriv_1/delta_1: should we generate 'TMatch
+  mark' or 'TMatch mark'? (neither is correct!)
+
+POSIX:
+   "(a?)*"   "b"    ""
+   "(a?)*"   "ab"   "a"
+   "((a)|(b))*"   "ab"  -> "b" none "b"
+Str
+   "(a?)*"   "b"    no submatch
+   "(a?)*"   "ab"   "a"
+   "((a)|(b))*"   "ab"  -> "b" "a" "b"
+Javascript
+   "(a?)*"   "b"    no submatch
+   "(a?)*"   "ab"   "a"
+   "((a)|(b))*"   "ab"  -> "b" none "b"
+PCRE
+   "(a?)*"   "b"    ""
+   "(a?)*"   "ab"   ""
+   "(a?)*?"  "b"    ""
+   "(a?)*?"  "ab"   "a"
+   "((a)|(b))*"   "ab"  -> "b" "a" "b"
+Emacs
+   "(a?)*"   "b"    ""
+   "(a?)*"   "ab"   ""
+   "(a?)*?"   "b"    ""
+   "(a?)*?"   "ab"   "a"
+   "((a)|(b))*"   "ab"  -> "b" "a" "b"
+
+
+  r{0,0}  = eps
+  r{i+1,j+1} = r,r{i,j}
+  r{0,j+1} = r,r{0,j} | eps            PCRE/Emacs
+  r{0,j+1} = (r-eps},r{0,j} | eps      JavaScript
+
+* Rewrite sequences of sequences when possible...
+
+High priority
+=============
+* Improve the Perl regular expressions parser
+* Character classes (in the three regular expression parsers)
+
+* Reduce memory usage
+  - More compact representation of character sequences
+  - Special notation for "anything but this set of characters"
+  (more generally, optimize the compilation of regular expressions)
+* Simple optimisations
+  - alt containing alt
+  - epsilon elimination
+  - Seq (Seq (x,y), z) => Seq (x, Seq (y, z)) under some circumstances
+    (x or y has a fixed length)
+  ...
+
+* Test suite
+
+Medium priority
+===============
+* Implement back-references
+* Implement look-ahead and look-behind assertions
+
+Low priority
+============
+* Optimize the main loop for processor that are not register starved
+* Rewrite the main loops in C
+  (but keep the option to compile a pure OCaml version)
+* Limit the size of the cached DFAs by removing states that have not
+  been used recently
+* Documentation
+
+Other ideas
+===========
+* It would be great to have a more generic interface (parameterized
+  over some abstract tokens).
+* Compile checked printers parameterized over match groups (DRY for
+  literal subexpressions)