lexer | Base library for a lexer that can be used in Top-Down, Recursive Descent Parsers | Parser library

 by   doctrine PHP Version: 3.0.0 License: MIT

kandi X-RAY | lexer Summary

kandi X-RAY | lexer Summary

lexer is a PHP library typically used in Utilities, Parser applications. lexer has no bugs, it has a Permissive License and it has medium support. However lexer has 1 vulnerabilities. You can download it from GitHub.

Base library for a lexer that can be used in Top-Down, Recursive Descent Parsers. This lexer is used in Doctrine Annotations and in Doctrine ORM (DQL).
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            kandi-support Support

              lexer has a medium active ecosystem.
              It has 10888 star(s) with 53 fork(s). There are 22 watchers for this library.
              OutlinedDot
              It had no major release in the last 12 months.
              There are 2 open issues and 8 have been closed. On average issues are closed in 42 days. There are no pull requests.
              It has a neutral sentiment in the developer community.
              The latest version of lexer is 3.0.0

            kandi-Quality Quality

              lexer has 0 bugs and 0 code smells.

            kandi-Security Security

              lexer has 1 vulnerability issues reported (0 critical, 1 high, 0 medium, 0 low).
              lexer code analysis shows 0 unresolved vulnerabilities.
              There are 0 security hotspots that need review.

            kandi-License License

              lexer is licensed under the MIT License. This license is Permissive.
              Permissive licenses have the least restrictions, and you can use them in most projects.

            kandi-Reuse Reuse

              lexer releases are available to install and integrate.
              lexer saves you 49 person hours of effort in developing the same functionality from scratch.
              It has 144 lines of code, 18 functions and 2 files.
              It has high code complexity. Code complexity directly impacts maintainability of the code.

            Top functions reviewed by kandi - BETA

            kandi has reviewed lexer and discovered the below as its top functions. This is intended to give you an instant insight into lexer implemented functionality, and help decide if they suit your requirements.
            • Scan input string for tokens .
            • Returns the literal for the given token .
            • Moves the pointer to the next token .
            • Set the input .
            • Returns the next token .
            • Get peek .
            • Reset the parser .
            • Skips until the given type .
            • Reset current position .
            • Returns true if the next token matches the given list of tokens .
            Get all kandi verified functions for this library.

            lexer Key Features

            No Key Features are available at this moment for lexer.

            lexer Examples and Code Snippets

            No Code Snippets are available at this moment for lexer.

            Community Discussions

            QUESTION

            PIP failed to build package cytoolz
            Asked 2022-Mar-26 at 18:26

            I'm trying to install eth-brownie using 'pipx install eth-brownie' but I get an error saying

            ...

            ANSWER

            Answered 2022-Jan-02 at 09:59

            I used pip install eth-brownie and it worked fine, I didnt need to downgrade. Im new to this maybe I could be wrong but it worked fine with me.

            Source https://stackoverflow.com/questions/69875694

            QUESTION

            yq - issue adding yaml into yaml
            Asked 2022-Mar-13 at 17:51

            Hi I would like to update a yaml like string into a yaml

            i do have the following yaml file argocd.yaml

            ...

            ANSWER

            Answered 2021-Oct-21 at 06:20

            Your second approach can work, but in a roundabout way, as mikefarah/yq does not support updating multi-line block literals yet

            One way to solve this, with the existing constructs would be to do below, without having to create a temporary YAML file

            Source https://stackoverflow.com/questions/69648216

            QUESTION

            How to parse recusrive grammar in FParsec
            Asked 2022-Mar-02 at 22:34

            Previous questions which I could not use to get this to work

            Recursive grammars in FParsec

            • Seems to be an old question which was asked before createParserForwardedToRef was added to FParsec
            • AST doesn't seem to be as horribly recursive as mine.

            Parsing in to a recursive data structure

            • Grammar relies on a special character '[' to indicate another nesting level. I don't have this luxury

            I want to build a sort of Lexer and project system for a language I have found myself writing lately. The language is called q. It is a fairly simple language and has no operator precedence. For example 1*2+3 is the same as (1*(2+3)). It works a bit like a reverse polish notation calculator, evaluation is right to left.

            I am having trouble expressing this in FParsec. I have put together the following simplified demo

            ...

            ANSWER

            Answered 2022-Mar-02 at 22:34

            Meditating on Tomas' answer, I have come up with the following that works

            Source https://stackoverflow.com/questions/71328877

            QUESTION

            Type Sedlexing.lexbuf is not compatible with type Lexing.lexbuf
            Asked 2022-Feb-19 at 11:20

            I would like to add incremental API and error handling of menhir to my project by sedlex+menhir; I'm trying to adopt attempt2 and fail of this sample to my code. Here is the attempt2 of the sample:

            ...

            ANSWER

            Answered 2022-Feb-19 at 11:20

            QUESTION

            Why would I use a lexer and not directly parse code?
            Asked 2022-Feb-08 at 10:44

            I am trying to create a simple programming language from scratch (interpreter) but I wonder why I should use a lexer. For me, it looks like it would be easier to create a parser that directly parses the code. what am I overlooking?

            ...

            ANSWER

            Answered 2022-Feb-08 at 10:44

            I think you'll agree that most languages (likely including the one you are implementing) have conceptual tokens:

            • operators, e.g * (usually multiply), '(', ')', ;
            • keywords, e.g., "IF", "GOTO"
            • identifiers, e.g. FOO, count, ...
            • numbers, e.g. 0, -527.23E-41
            • comments, e.g., /* this text is ignored in your file */
            • whitespace, e.g., sequences of blanks, tabs and newlines, that are ignored

            As a practical matter, it takes a specific chunk of code to scan for/collect the characters that make each individual token. You'll need such a code chunk for each type of token your language has.

            If you write a parser without a lexer, at each point where your parser is trying to decide what comes next, you'll have to have ALL the code that recognize the tokens that might occur at that point in the parse. At the next parser point, you'll need all the code to recognize the tokens that are possible there. This gives you an immense amount of code duplication; how many times do you want the code for blanks to occur in your parser?

            If you think that's not a good way, the obvious cure to is remove all the duplication: place the code for each token in a subroutine for that token, and at each parser place, call the subroutines for the tokens. At this point, in some sense, you already have a lexer: an isolated collection of code to recognize tokens. You can code perfectly fine recursive descent parsers this way.

            The next thing you'll discover is that you call the token subroutines for many of the tokens at each parser point. Even that seems like a lot of work and duplication. So, replace all the calls with a single "GetNextToken" call, that itself invokes the token recognizing code for all tokens, and returns a enum that identifies the specific token encountered. Now your parser starts to look reasonable: at each parser point, it makes one call on GetNextToken, and then branches on enum returned. This is basically the interface that people have standardized on as a "lexer".

            One thing you will discover is the token-lexers sometimes have trouble with overlaps; keywords and identifiers usually have this trouble. It is actually easier to merge all the token recognizers into a single finite state machine, which can then distinguish the tokens more easily. This also turns out to be spectacularly fast when processing the programming language source text. Your toy language may never parse more than 100 lines, but real compilers process millions of lines of code a day, and most of that time is spent doing token recognition ("lexing") esp. white space suppression.

            You can code this state machine by hand. This isn't hard, but it is rather tedious. Or, you can use a tool like FLEX to do it for you, that's just a matter of convenience. As the number of different kinds of tokens in your language grows, the FLEX solution gets more and more attractive.

            TLDR: Your parser is easier to write, and less bulky, if you use a lexer. In addition, if you compile the individual lexemes into a state machine (by hand or using a "lexer generator"), it will run faster and that's important.

            Source https://stackoverflow.com/questions/70460557

            QUESTION

            how to distinguish tokens which have similar patterns in Lexer, but they occur in different contexts in the parser
            Asked 2021-Dec-30 at 13:16

            I have two pretty similar patterns in Lexer.x first for numbers second for byte. Here they are.

            ...

            ANSWER

            Answered 2021-Dec-30 at 13:16

            In that case you should postpone parsing. You can for example make a TNumByte data constructor that stores the value as String:

            Source https://stackoverflow.com/questions/70525997

            QUESTION

            How does Python interpreter actually interpret a program?
            Asked 2021-Dec-29 at 07:59

            Take a sample program:

            ...

            ANSWER

            Answered 2021-Dec-29 at 03:13

            The problem is not the order of interpretation, which is top to bottom as you expect; it's the scope. In Python, when referencing a global variable in a narrower function scope, if you modify the value, you must first tell the code that the global variable is the variable you are referencing, instead of a new local one. You do this with the global keyword. In this example, your program should actually look like this:

            Source https://stackoverflow.com/questions/70514761

            QUESTION

            Initialized declarator inside of C++ catch statement
            Asked 2021-Dec-13 at 15:54

            Do you think that the initialized declarator is a valid lexical structure inside of the caught-declaration part of the catch statement? For example, take a look at the following code:

            ...

            ANSWER

            Answered 2021-Dec-13 at 15:07

            first: No the article does not says it allows initializer in catch statement.

            It says to refer to the function specification for

            • type-specifier-seq
            • declarator
            • abstract-declarator

            or the initializer is a different element.

            Second:

            An initializer in a catch statement is pointless since a value is required for actualy going into a catch statement. which means that the initializer value would never be used, and it would jeopardize the program flow since the initalization could raise an exception that will at best terminate.

            MSVC probably tolerate it out of pointlessness since it cannot affect the program

            Source https://stackoverflow.com/questions/70336370

            QUESTION

            Handling end of file
            Asked 2021-Nov-25 at 20:13

            I am trying to write a reentrant C++ parser with bison, I followed the Complete C++ Example and I am using bison 3.5.1 and flex 2.6.4 (the versions available via apt-get in ubuntu buster).

            After completing I had an issue in the lexer ‘make_YYEOF’ is not a member of ‘yy::parser’

            My solution to that was to declare %token YYEOF

            Then it compiles but the parser gives the syntax error, unexpected YYEOF, expecting $end, for an apparently valid input.

            Then I made the simplified rule unit: IDENTIFIER YYEOF but again, the parser reports the same error.

            ...

            ANSWER

            Answered 2021-Nov-25 at 20:09

            That problem is solved by declaring

            Source https://stackoverflow.com/questions/70093333

            QUESTION

            How to leave out unimportant nodes?
            Asked 2021-Oct-27 at 23:16

            I am using ANTLR 4.9.2 to parse a grammar that represents assembly instructions.

            ...

            ANSWER

            Answered 2021-Oct-27 at 06:23

            Your question boils down to: "how can I convert my parse tree to an abstract syntax tree?". The simple answer to that is: "you can't" :). At least, not using a built-in ANTLR mechanism. You'll have to traverse the parse tree (using ANTLR's visitor- or listener mechanism) and construct your AST manually.

            The feature to more easily create AST's from a parse tree often pops up both in ANTLR's Github repo:

            as well as on stackoverflow:

            Source https://stackoverflow.com/questions/69732452

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

            Vulnerabilities

            No vulnerabilities reported

            Install lexer

            You can download it from GitHub.
            PHP requires the Visual C runtime (CRT). The Microsoft Visual C++ Redistributable for Visual Studio 2019 is suitable for all these PHP versions, see visualstudio.microsoft.com. You MUST download the x86 CRT for PHP x86 builds and the x64 CRT for PHP x64 builds. The CRT installer supports the /quiet and /norestart command-line switches, so you can also script it.

            Support

            For any new features, suggestions and bugs create an issue on GitHub. If you have any questions check and ask questions on community page Stack Overflow .
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            https://github.com/doctrine/lexer.git

          • CLI

            gh repo clone doctrine/lexer

          • sshUrl

            git@github.com:doctrine/lexer.git

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