lexpp

Small Extremely Powerful Header Only C++ Lexical Analyzer/String Parser Library

Lexpp is made with simplicity and size in mind. The entire library is about 500 lines!

Lexpp is very powerful and can be used for almost all parsing needs!

You can check the examples/ for more elaborate usage.

Docs :

https://github.com/Jaysmito101/lexpp/wiki

For any help join our discord server https://discord.gg/muq5nDxF9t

How to Use

Just place the lexpp.h file in your project include directory.

In one cpp file define LEXPP_IMPLEMENTATION before importing lexpp like this:

#define LEXPP_IMPLEMENTATION
#include "lexpp.h"

You are all done to use lexpp!

Basic Examples

String parsing

Click To See Code

std::string data = "some text to parse! ";
std::vector<std::string> tokens = lexpp::lex(data, {"<=", "<<", "\n", "::", ",", "}", "{", ";", " "}, false);

for(std::string& token : tokens){
    std::cout << token << std::endl;
}

Using Custom Token Classifier

Some Structs we will need

Click To See Code

enum MyTokens{
    Keyword = 0,
    Number,
    String,
    Other
};

static std::string TokenToString(int tok){
switch(tok){
    case Keyword: return "Keyword";
    case Number:  return "Number";
    case String:  return "String";
    case Other:   return "Other";
}
}

Now the Lexing

Click To See Code

std::vector<std::string> keywords = {"for", "void", "return", "if", "int"};
std::vector<lexpp::Token> tokens = lexpp::lex(data, {"<=", "<<", "\n", "::", ",", "}", "{", "(", ")" ";", " "}, [keywords](std::string& token, bool* discard, bool is_separator) -> int {
    if(std::find(keywords.begin(), keywords.end(), token) != keywords.end()){
        return MyTokens::Keyword;
    }
    if(is_number(token))
        return MyTokens::Number;
    else
        return MyTokens::String;
}, false);

for(lexpp::Token& token : tokens){
    std::cout << TokenToString(token.type) << " -> " << token.value << std::endl;
}

Using the TokenParser class

We need to extend the TokenParser class to have our cuastom token parser

Click To See Code

class MyTokenParser : public lexpp::TokenParser
{
public:
MyTokenParser(std::string data, std::string separators)
:TokenParser(data, separators, false){}

virtual int process_token(std::string& token, bool* discard, bool isSeparator) override
{
    if(std::find(keywords.begin(), keywords.end(), token) != keywords.end())
        return MyTokens::Keyword;
    else if(is_number(token))
        return MyTokens::Number;
    else if(isSeparator)
        return MyTokens::Other;
    else
        return MyTokens::String;
}    

std::vector<std::string> keywords = {"for", "void", "return", "if", "int"};
};

Now using the class with the lexer

Click To See Code

std::vector<lexpp::Token> tokens =     lexpp::lex(std::make_shared<MyTokenParser>(data, "\n :,[]{}().\t"));
for(lexpp::Token& token : tokens){
    std::cout << TokenToString(token.type) << " -> " << token.value << std::endl;
}

Making an email parser with lexpp

First a struct to store out data

Click To See Code

struct Email{
    std::string name;
    std::string domainFront;
    std::string domainEnd;
    std::string domain;
};

Now we need to make our custom token parser for email parsing

Click To See Code

class EmailTokenParser : public lexpp::TokenParser
{
public:
EmailTokenParser(std::string data, std::string separators = "\n@.")
:TokenParser(data, separators, true){}

virtual int process_token(std::string& token, bool* discard, bool isSeparator) override
{
    if(isSeparator){
        if(ci == 2){
            currMail.domain = currMail.domainFront + "." + currMail.domainEnd;
            emailIds.push_back(currMail);
            ci = 0;
            *discard = true;
            return 0;  
        }
        if(token.size() <= 0){
            *discard = true;
            return 0;  
        }
        if(token == "\n"){
            ci = 0;
            *discard = true;
            return 0;  
        }
        else if(token == "@"){
            ci = 1;
            *discard = true;
            return 0;                
        }
        else if(token == "."){
            ci = 2;
            *discard = true;
            return 0;                
        }
    }

    if(ci == 0)
        currMail.name = token;
    else if(ci == 1)
        currMail.domainFront = token;
    else if(ci == 2)
        currMail.domainEnd = token;
}    

int ci = 0;
Email currMail;
std::vector<Email> emailIds;
};

Now finally calling lex

Click To See Code

std::shared_ptr<EmailTokenParser> tok_parser = std::make_shared<EmailTokenParser>(data+"\n", "\n@.");
lexpp::lex(tok_parser);
for(Email& email : tok_parser->emailIds){
    std::cout << "Email : \nNAME: " << email.name << "\nDOMAIN : " << email.domain << std::endl;
}

Support

I am just a Highschool student so I may not have the best quality of code but still i am trying my best to write good code!

Any support would be highly appretiated!

For example you could add a feature and contribute via pull requests or you could even report any issues with the program!

And the best thing you could do to support this project is spread word about this so that more people who might be interested in this may use this!

Please considering tweeting about this!