JFlex | Java version of Flex | Object-Relational Mapping library

One way to do this is to use states in JFlex. We say that every time the word co is matched, we enter in a state named COMMENT_STATE and we do nothing until the end of the line. After the end of the line, we exit the COMMENT_STATE state. So here is the code:

The regular expression you copied is for (f)lex, which uses a slightly different syntax for regular expressions. In particular, (f)lex treats " as an ordinary character inside bracketed classes, so [^"\\] is a character class matching anything other than (^) a quotation mark (") or a backslash (\\).

However, in JFlex, the " is a quoting character, whether outside or inside brackets. So the " in the character class is unterminated. Hence the error message.

So you need to backslash-escape it:

I openned two JIRA to understand this problem. See the links below:

1. https://datastax-oss.atlassian.net/browse/SPARKC-652
2. https://datastax-oss.atlassian.net/browse/JAVA-2945

You've basically deciphered it correctly. Here's a few explanatory notes:

[^]* matches an arbitrary sequence of characters. It's similar to .* except that . doesn't match newlines or unpaired surrogates; [^] matches absolutely anything.

So ([^]* "*/" [^]*) matches any sequence which includes */. And therefore !([^]* "*/" [^]*) matches anything except a sequence containing */. In other words, it matches anything up to but not including */, which is the rest of the comment.

Now what happens if the user makes a mistake and forgets to close the last comment? In that case, there is no */ and will match up to the end of input. Since there's no way to know where the comment should have ended (without being able to read the programmer's mind), the best we can do is to stop trying to parse. Thus, we accept the unterminated comment as a comment. That's why the final "*/"? is optional. It will match the comment terminator if there is one, and otherwise it will match an empty sequence at the end of the input.

Regular expression based lexical analysis is really not the right tool to parse fixed-field inputs. You can just split the input into fields at the known character positions, which is way easier and a lot faster. And it doesn't require fussing with regular expressions.

Anyway, [a-zA-Z][a-zA-Z0-9]{0,14}[ ]{0,14} wouldn't be the right expression even if it did properly handle the token length, since the token is really the word at the beginning, without space characters.

In the case of fixed-length fields which contain something more complicated than a single identifier, you might want to feed the field into a lexer, using a StringReader or some such.

Although I'm sure it's not useful, here's a regular expression which matches 15 characters which start with a word and are completed with spaces:

CUP is a LALR parser generator, which means that there is no need to avoid left-recursion and so you can use a more natural grammatical style; there is no need to split lists into "start" and "continuation" productions, which are hard to read and error-prone, and furthermore often do not allow the direct construction of an accurate syntax tree.

There are lots of conflicts in your grammar, but this one is clearly ambiguous:

The idea is to find the correctly written operators not ifo or elso. Thanks in advance.

Just use "if" and "else" and have another pattern that would match ifo and elseo (like for identifiers) and that comes after the patterns for if and else:

This can be achieved by omitting the %standalone tag at the top of the jflex file. This makes jflex not generate the default main() method and allows the user to set their own custom main() method inside of a %{ %} code segment.

Within this main(), the user can place the original code for the autogenerated main(), but can update to the desired outcome.

Within this context:

You can run all the Windows 10 executables including Java from within WSL, but note that GNU/Linux won't tack on ".EXE" by default as Windows does (Windows uses PATHEXT=.COM;.EXE;.BAT ... for this purpose), and WSL won't necessarily have the Windows binaries on the bash PATH.

For example my installation of JDK14 is at Windows C:\java\jdk-14 == WSL /mnt/c/java/jdk-14: