jflex | fast scanner generator for Java™ with full Unicode support | Regex library
kandi X-RAY | jflex Summary
kandi X-RAY | jflex Summary
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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Top functions reviewed by kandi - BETA
- 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 .
jflex Key Features
jflex Examples and Code Snippets
License : Strong Copyleft (CC BY-SA 4.0)
Copy 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 + "\'"
elsimport 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@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@State(Scope.Benchmark)
@BenchmarkMode(Mode.Throughput)
@Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@OutputTimeUnit(TimeUnit.MILLISECONDSjmh {
warmupIterations = 2
iterations = 5
fork = 1
jvmArgsPrepend = ['-XX:+UnlockDiagnosticVMOptions', '-XX:-UseMultiplyToLenIntrinsic']
}
Benchmark Mode Cnt Score 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) {
iConsumer consumer = switch (event.getEventType()) {
case ORDER -> e -> handle((OrderEvent) e);
case INVOICE -> e -> handle((InvoiceEvent) e);
case PAYMENT -> e -> handle((PaymentEvent) e);
};
consumer.accept(elibrary(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_s7-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 @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(woCommunity Discussions
Trending Discussions on jflex
QUESTION
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 18:16The 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.
QUESTION
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 11:06One 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:
QUESTION
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 20:46The 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:
QUESTION
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 23:23I openned two JIRA to understand this problem. See the links below:
QUESTION
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 20:49You'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.
QUESTION
Given a positional language like the old IBM RPG, we can have a line such as
...ANSWER
Answered 2021-May-17 at 03:53Regular 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:
QUESTION
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 02:50CUP 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:
QUESTION
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 13:30The 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:
QUESTION
In Jflex, how does one extract the input filename?
DisplayFilename.jflex:
...ANSWER
Answered 2021-Apr-08 at 22:08This 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:
QUESTION
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 10:54You 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:
Community Discussions, Code Snippets contain sources that include Stack Exchange Network
Vulnerabilities
No vulnerabilities reported
Install jflex
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.
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