Tag Archives: sets

Polishing the parser generator

The best way to get a reason for improvement is using your own program — currently I constantly switch between Skila and NLT parser generator, because every feature I add makes my work on Skila much easier.

I added types definitions, so no longer I have to cast the symbol objects in the code blocks:

  expression Expression;
  IDENTIFIER IdentifierSymbol;

With such definitions I can use symbol object “expression” and C# code will know it is of type “Expression”.

With sets and sequences I can reduce amount of rules significantly — sets:

fparam -> [ r:REF s:SINK e:EXCL ]? id:IDENTIFIER 
          { new FunctionParameter(...) };

Here we see an optional set (very similar notion to regular expressions) — identifier can be preceded by “PARAM_REF” or “SINK” or “EXCLAMATION” or (set above is optional) nothing.

Once I implemented set, sequence was an obvious addition:

field -> id:IDENTIFIER t:type (EQ ex:expression)?
         { new ClassField(...) };

Type can be followed by “ASSIGN” and “expression”. Unlike set it is everything (entire sequence in given order) or — in case of optional sequence, like here — nothing.

On Skila front I made some progress working on reference types (class) but finishing it will take some more time.

Tagged , , ,