GLR is great if you want a parse tree/forest and don’t mind black boxes. It lets you type in whatever CFG you want at the cost of checking for ambiguities at parse time via exhaustive testing, instead of resolving LR/LALR conflicts statically. Some say that’s a good trade-off. Ira Baxter’s DMS tool or Elkhound, which … Read more
It really depends what you start with and what you want to do. There isn’t a one size fits all. If have an LR grammar (e.g. you are working from a Yacc grammar), it is a good deal of work to turn it into an LL one suitable for Parsec or uu-parsinglib. However the many, … Read more
At a high level, the difference between LR(0), LALR(1), and LR(1) is the following: An LALR(1) parser is an “upgraded” version of an LR(0) parser that keeps track of more precise information to disambiguate the grammar. An LR(1) parser is a significantly more powerful parser that keeps track of even more precise information than an … Read more
You can slice off the last character: read_line = read_line[:len(read_line)-1] Perhaps a better approach is to use the strings library: read_line = strings.TrimSuffix(read_line, “\n”)
You should know how to build recursive descent parsers by hand. Here’s an SO link to a quick lesson on how to do this: https://stackoverflow.com/a/2336769/120163 If you want to understand how recursive descent parsers can be constructed automatically, you can read a paper (and see a tutorial) on MetaII at this link: https://stackoverflow.com/a/1142034/120163
The abstraction for the IFormFile has an .OpenReadStream method. To prevent a ton of undesirable and potentially large allocations, we should read a single line at a time and build up our list from each line that we read. Additionally, we could encapsulate this logic in an extension method. The Index action ends up looking … Read more
Left factoring is removing the common left factor that appears in two productions of the same non-terminal. It is done to avoid back-tracing by the parser. Suppose the parser has a look-ahead, consider this example: A -> qB | qC where A, B and C are non-terminals and q is a sentence. In this case, … Read more
Depending on the shell you are using, you can turn the approach @Blair suggested into a 1-liner diff <(cut -b13- file1) <(cut -b13- file2) (+1 to @Blair for the original suggestion 🙂
Examples from wikipedia LL(1) grammar S -> F S -> ( S + F ) F -> a input ( a + a ) parsing steps S -> “(” S “+” F “)” -> ( “F” + F ) -> ( “a” + F ) -> ( a + “a” ) LR(0) grammar (1) E … Read more