jflex | fast scanner generator for Java™ with full Unicode support | Regex library

 by   jflex-de Java Version: v1.9.1 License: Non-SPDX

kandi X-RAY | jflex Summary

kandi X-RAY | jflex Summary

jflex is a Java library typically used in Utilities, Regex applications. jflex has no bugs, it has no vulnerabilities, it has build file available and it has high support. However jflex has a Non-SPDX License. You can download it from GitHub, Maven.

JFlex is a lexical analyzer generator (also known as scanner generator) for Java. JFlex takes as input a specification with a set of regular expressions and corresponding actions. It generates Java source of a lexer that reads input, matches the input against the regular expressions in the spec file, and runs the corresponding action if a regular expression matched. Lexers usually are the first front-end step in compilers, matching keywords, comments, operators, etc, and generating an input token stream for parsers. JFlex lexers are based on deterministic finite automata (DFAs). They are fast, without expensive backtracking.
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            kandi-support Support

              jflex has a highly active ecosystem.
              It has 531 star(s) with 109 fork(s). There are 23 watchers for this library.
              OutlinedDot
              It had no major release in the last 12 months.
              There are 23 open issues and 304 have been closed. On average issues are closed in 907 days. There are 6 open pull requests and 0 closed requests.
              OutlinedDot
              It has a negative sentiment in the developer community.
              The latest version of jflex is v1.9.1

            kandi-Quality Quality

              jflex has 0 bugs and 0 code smells.

            kandi-Security Security

              jflex has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.
              jflex code analysis shows 0 unresolved vulnerabilities.
              There are 0 security hotspots that need review.

            kandi-License License

              jflex has a Non-SPDX License.
              Non-SPDX licenses can be open source with a non SPDX compliant license, or non open source licenses, and you need to review them closely before use.

            kandi-Reuse Reuse

              jflex releases are available to install and integrate.
              Deployable package is available in Maven.
              Build file is available. You can build the component from source.
              Installation instructions, examples and code snippets are available.
              jflex saves you 1409433 person hours of effort in developing the same functionality from scratch.
              It has 615684 lines of code, 2479 functions and 485 files.
              It has medium code complexity. Code complexity directly impacts maintainability of the code.

            Top functions reviewed by kandi - BETA

            kandi has reviewed jflex and discovered the below as its top functions. This is intended to give you an instant insight into jflex implemented functionality, and help decide if they suit your requirements.
            • Minimize the DFA .
            • Initializes the unicode data .
            • Emit a lexical function header .
            • Parses the command line arguments .
            • Walk the given item .
            • Setup the components .
            • Returns an array of productions for a given LHS .
            • Build the GUI .
            • Checks that the parameters of a given action match the given position .
            • Creates a DFA from nfa .
            Get all kandi verified functions for this library.

            jflex Key Features

            No Key Features are available at this moment for jflex.

            jflex Examples and Code Snippets

            Aggregate rows of Spark RDD to String after groupby
            Lines of Code : 35dot img1License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
               def listToString(s): 
                
                # initialize an empty string    str1 += ele
                str1 = "" 
                cnt = 0
                
                # traverse in the string  
                for ele in s: 
                    if cnt == 0:
                      str1 += "\'" + ele + "\'"
                      
                    els
            JMH - How to measure time it takes to insert 50M items in an ArrayList
            Javadot img2Lines of Code : 93dot img2License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            import java.util.List;
            import java.util.ArrayList;
            
            import org.openjdk.jmh.annotations.Benchmark;
            import org.openjdk.jmh.annotations.Level;
            import org.openjdk.jmh.annotations.Param;
            import org.openjdk.jmh.annotations.Scope;
            import org.open
            looping over array, performance difference between indexed and enhanced for loop
            Javadot img3Lines of Code : 87dot img3License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            @Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
            @Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
            @Fork(3)
            @BenchmarkMode(Mode.AverageTime)
            @OutputTimeUnit(TimeUnit.NANOSECONDS)
            @State(Scope.Benchmark)
            publ
            OutOfMemoryError when benchmarking ArrayList.add() in JMH
            Javadot img4Lines of Code : 37dot img4License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            @State(Scope.Benchmark)
            @BenchmarkMode(Mode.Throughput)
            @Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
            @Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
            @OutputTimeUnit(TimeUnit.MILLISECONDS
            Java BigInteger source code performance benchmark
            Javadot img5Lines of Code : 11dot img5License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            jmh {
                warmupIterations = 2 
                iterations = 5 
                fork = 1 
                jvmArgsPrepend = ['-XX:+UnlockDiagnosticVMOptions', '-XX:-UseMultiplyToLenIntrinsic']
            }
            
            Benchmark                        Mode  Cnt       Score  
            No ConcurrentModificationException during index based iteration
            Javadot img6Lines of Code : 90dot img6License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            public static void main(String[] args) {
                List input = new ArrayList<>();
                List output = new ArrayList<>();
                for(int i=0; i< 1000 ;i++){
                    input.add(i+"");
                }
                
                for (String value : input) {
                    i
            Switch expression with void return type
            Javadot img7Lines of Code : 162dot img7License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            Consumer consumer = switch (event.getEventType()) {
                case ORDER -> e -> handle((OrderEvent) e);
                case INVOICE -> e -> handle((InvoiceEvent) e);
                case PAYMENT -> e -> handle((PaymentEvent) e);
            };
            consumer.accept(e
            pipeops makes paramter not available for tuning in mlr3proba
            Lines of Code : 140dot img8License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            library(mlr3proba)
            library(mlr3)
            library(paradox)
            library(mlr3tuning)
            library(mlr3extralearners)
            library(mlr3pipelines)
            
            task.mlr <- tsk("rats")
            inner.rsmp <- rsmp("holdout")
            measure <- msr("surv.cindex")
            tuner <- tnr("random_s
            How can I check if .tar (not tar.gz) file is corrupt or not, in Ubuntu?
            Lines of Code : 108dot img9License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            7-Zip [64] 17.03 : Copyright (c) 1999-2020 Igor Pavlov : 2017-08-28
            p7zip Version 17.03 (locale=en_US.UTF-8,Utf16=on,HugeFiles=on,64 bits,4 CPUs x64)
            
            Usage: 7z  [...]  [...]
            
            
              a : Add files to archive
              b : Benchmark
              d : Delete files 
            Why is iteration is faster than Streams in Java?
            Javadot img10Lines of Code : 38dot img10License : Strong Copyleft (CC BY-SA 4.0)
            copy iconCopy
            @BenchmarkMode(Mode.AverageTime)
            @OutputTimeUnit(TimeUnit.MILLISECONDS)
            @State(Scope.Benchmark)
            public class Streams {
                String[] words;
            
                @Setup
                public void setup() {
                    words = new String[10_000_000];
                    Arrays.fill(wo

            Community Discussions

            QUESTION

            Jflex and CUP not working on vscode and mac
            Asked 2022-Feb-22 at 18:16

            I downloaded jflex by doing brew install jflex everything worked the way it should.

            But now when I'm trying to make it work with java_cup.runtime.*. And I keep getting the errors below

            ...

            ANSWER

            Answered 2022-Feb-22 at 18:16

            The fix for this issue is that if you use %cup in your jflex file you must then make your own sym class which contains public static final int EOF=0.

            Source https://stackoverflow.com/questions/71180011

            QUESTION

            check if condition is met before executing the action in JFlex
            Asked 2021-Oct-17 at 11:06

            I am writing a lexical analyzer using JFlex. When the word co is matched, we have to ignore what comes after until the end of the line (because it's a comment). For the moment, I have a boolean variable that changes to true whenever this word is matched and if an identifier or an operator is matched after co until the end of the line, I simply ignore it because I have an if condition in my Identifier and Operator token identification.
            I am wondering if there is better way to do this and get rid of this if statement that appears everywhere?

            Here is the code:

            ...

            ANSWER

            Answered 2021-Oct-17 at 11:06

            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:

            Source https://stackoverflow.com/questions/69603028

            QUESTION

            JLEX lexical generator error: unterminated string at the end of the line
            Asked 2021-Jun-15 at 20:46

            I am generating lexical analyzer with JLEX. I found a regular expression for string literal from this link and used it in .jflex file same of other expressions. but it gives me this error : unterminated string at the end of the line
            StringLiteral = \"(\\.|[^"\\])*\"

            can anyone help me please, thanks.

            ...

            ANSWER

            Answered 2021-Jun-15 at 20:46

            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:

            Source https://stackoverflow.com/questions/67991038

            QUESTION

            Cassandra with spark : java.io.IOException: Failed to open native connection to Cassandra at {127.0.0.1:9042} ::
            Asked 2021-May-25 at 23:23

            I have an application using Boot Strap running with cassandra 4.0, Cassandra java drive 4.11.1, spark 3.1.1 into ubuntu 20.4 with jdk 8_292 and python 3.6.

            When I run a function that it call CQL by spark, the tomcat gave me the error bellow.

            Stack trace:

            ...

            ANSWER

            Answered 2021-May-25 at 23:23

            QUESTION

            Explanation of JFlex Block Comment rule
            Asked 2021-May-23 at 20:49

            I was looking on how to implement block comments in JFlex for custom language support in intellij and found that it can be described as

            ...

            ANSWER

            Answered 2021-May-23 at 20:49

            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.

            Source https://stackoverflow.com/questions/67661631

            QUESTION

            JFlex maximum read length
            Asked 2021-May-17 at 03:53

            Given a positional language like the old IBM RPG, we can have a line such as

            ...

            ANSWER

            Answered 2021-May-17 at 03:53

            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:

            Source https://stackoverflow.com/questions/67558980

            QUESTION

            Ambiguous Context-free grammar? / Shift/Reduce conflict in CUP
            Asked 2021-May-04 at 02:50

            I have the following context-free grammar for a simplified version of C++. When I run it with JFLEX and CUP I get a list of errors like that:

            ...

            ANSWER

            Answered 2021-May-04 at 02:50

            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:

            Source https://stackoverflow.com/questions/67377172

            QUESTION

            Is there an alternative to \b and/or negative lookahead for JFLEX?
            Asked 2021-Apr-14 at 13:30

            I am building a Scanner and can't seem to find a way to identify operators like "if" or "else" using JFlex & Regex. Since JFlex doesn't fully conform I can't use word-boundary or (?<=\s|^) + (?=\s|$) because neither ? or $ are allowed. The idea is to find the correctly written operators not ifo or elso. Thanks in advance.

            ...

            ANSWER

            Answered 2021-Apr-14 at 13:30

            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:

            Source https://stackoverflow.com/questions/67083803

            QUESTION

            Jflex get input filename
            Asked 2021-Apr-08 at 22:08

            In Jflex, how does one extract the input filename?

            DisplayFilename.jflex:

            ...

            ANSWER

            Answered 2021-Apr-08 at 22:08

            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:

            Source https://stackoverflow.com/questions/66934058

            QUESTION

            Using Ubuntu's subsystem on Windows for 'make' gives java error
            Asked 2021-Feb-11 at 10:54

            I am trying to execute Makefile as part of my course. It's a parser and lexer in CUP and Jflex, respectively. It is not possible to do it in Windows Powershell, so I was advised to use Linux, my colleague was also able to run it on Ubuntu's subsystem on Windows.

            So I downloaded the ubuntu:

            https://www.microsoft.com/en-us/p/ubuntu/9nblggh4msv6?activetab=pivot:overviewtab from MS Store

            Then allowed to use Linux subsystem in the Windows settings, however now, when I try to run make in bash, I get this error:

            ...

            ANSWER

            Answered 2021-Feb-11 at 10:54

            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:

            Source https://stackoverflow.com/questions/66144893

            Community Discussions, Code Snippets contain sources that include Stack Exchange Network

            Vulnerabilities

            No vulnerabilities reported

            Install jflex

            See Build tool plugins.
            JFlex can be built with Bazel. Migration to Bazel is still work in progress, concerning the test suite, for instance. This builds bazel-bin/jflex/jflex_bin, that you can use. Build uberjar (aka fatjar aka deploy jar). Continuous integration is done with Cirrus CI. You need JDK 8 or later. This generates jflex/target/jflex-full-1.9.0-SNAPSHOT.jar that you can use, e.g. Continuous Integration is made with Travis.

            Support

            JFlex is free software, contributions are welcome. See the Contributing page for instructions.
            Find more information at:

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