3 ms·

Why do you need to parse the language to get parens correct? For most languages, comments and strings will need to be considered, but neither of these requires

by dbaupp 10y ago

Why do you need to parse the language to get parens correct? For most languages, comments and strings will need to be considered, but neither of these requires doing a full parse. Of course, I don't disagree with your point that a fast parser makes making a distinction here less useful. However that number sounds interestingly large, without context, do you have more info I can read about it?

WorldMaker 10y ago
Parsers don't often handle degenerate cases very well, but degenerate cases are quite common in text editing. (Think about how often work in progress code might actually parse correctly.) Lexers/tokenizers handle degenerate cases very well (after many years of being used for syntax highlighting in IDEs), and some parsers intended for IDE consumption are getting much better at dealing with degenerate cases (the Roslyn family and Typescript in my experience have some very interesting work put into this area), but most parsers still have a long way to go. (Especially, because many of the most common parser-generators themselves have never bothered to concern themselves with degenerate cases.)
- dbaupp 10y ago
  You make a good point (not only is parsing unnecessary, lexing-only/"ad hoc" analysis can be more resilient for many of the tasks in an editor), however your phrasing makes it sound like you're disagreeing with me, but I don't understand with which part of my comment. Could you expand?
  - WorldMaker 10y ago
    Interesting. I'm not sure what tone you were seeing, other than I realize "degenerate" has a very negative tone, but is the most apt technical term I can find. Was neither agreeing nor disagreeing with your points, simply expanding "sideways", because I think the conversation about the usefulness of parsing to general usage in text editors and information processing gets derailed by the "degenerate" cases where things don't parse (because those are very important to text editors). I think people often forget or underappreciate the lexing half of the lexer/parser divide. Yet syntax highlighting engines in most of the text editors we use these days already hint that you can do a lot of user meaningful things with "just" rudimentary, generic lexers. As a continued aside: I felt I got really good results using a lexer as the basis for a character-based somewhat "semantic" diff tool, but still to date I've yet to really see it come into general usage outside my prototype toy (http://github.com/WorldMaker/tokdiff http://github.com/WorldMaker/tokdiff).

by dbaupp 10y ago

WorldMaker 10y ago

Parsers don't often handle degenerate cases very well, but degenerate cases are quite common in text editing. (Think about how often work in progress code might actually parse correctly.) Lexers/tokenizers handle degenerate cases very well (after many years of being used for syntax highlighting in IDEs), and some parsers intended for IDE consumption are getting much better at dealing with degenerate cases (the Roslyn family and Typescript in my experience have some very interesting work put into this area), but most parsers still have a long way to go. (Especially, because many of the most common parser-generators themselves have never bothered to concern themselves with degenerate cases.)

dbaupp 10y ago
You make a good point (not only is parsing unnecessary, lexing-only/"ad hoc" analysis can be more resilient for many of the tasks in an editor), however your phrasing makes it sound like you're disagreeing with me, but I don't understand with which part of my comment. Could you expand?
- WorldMaker 10y ago
  Interesting. I'm not sure what tone you were seeing, other than I realize "degenerate" has a very negative tone, but is the most apt technical term I can find. Was neither agreeing nor disagreeing with your points, simply expanding "sideways", because I think the conversation about the usefulness of parsing to general usage in text editors and information processing gets derailed by the "degenerate" cases where things don't parse (because those are very important to text editors). I think people often forget or underappreciate the lexing half of the lexer/parser divide. Yet syntax highlighting engines in most of the text editors we use these days already hint that you can do a lot of user meaningful things with "just" rudimentary, generic lexers. As a continued aside: I felt I got really good results using a lexer as the basis for a character-based somewhat "semantic" diff tool, but still to date I've yet to really see it come into general usage outside my prototype toy (http://github.com/WorldMaker/tokdiff http://github.com/WorldMaker/tokdiff).