Building a Regex Engine in Go: Introducing MatchGo

In today's programming landscape, regular expressions (regex) are invaluable tools for text processing, enabling developers to search, match, and manipulate strings with precision. I recently embarked on an exciting project to create a regex engine in Go, named MatchGo, utilizing a Non-deterministic Finite Automaton (NFA) approach. This blog post will walk you through the development journey of MatchGo, highlighting its features and practical usage.

Project Overview

MatchGo is an experimental regex engine designed for simplicity and ease of use. It allows you to compile regex patterns, check strings for matches, and extract matched groups. While it's still in development, I aimed to create a functional library that adheres to core regex principles, inspired by various resources and regex implementations.

Key Features

• Basic Syntax Support: MatchGo supports foundational regex constructs, including:

  • Anchors: ^ (beginning) and $ (end) of strings.
  • Wildcards: . to match any single character.
  • Character Classes: Bracket notation [ ] and negation [^ ].
  • Quantifiers: *, , ?, and {m,n} for specifying repetition.
  • Capturing Groups: ( ) for grouping and backreferences.

• Special Character Handling: MatchGo supports escape sequences and manages special characters in regex, ensuring accurate parsing and matching.

• Multiline Support: The engine has been tested with multiline inputs, where . does not match newlines (n), and $ correctly matches the end of lines.

• Error Handling: Improved error handling mechanisms to provide clear feedback during compilation and matching.

Installation

To incorporate MatchGo into your Go project, simply run the following command:

go get github.com/Ravikisha/matchgo

Usage

Getting started with MatchGo is straightforward. Here’s how you can compile a regex pattern and test it against a string:

import "github.com/Ravikisha/matchgo"

pattern, err := matchgo.Compile("your-regex-pattern")
if err != nil {
    // handle error
}

result := pattern.Test("your-string")
if result.Matches {
    // Access matched groups by name
    groupMatchString := result.Groups["group-name"]
}

To find all matches in a string, use FindMatches:

matches := pattern.FindMatches("your-string")
for _, match := range matches {
    // Process each match
    if match.Matches {
        fmt.Println("Match found:", match.Groups)
    }
}

Example Code

Here’s a practical example demonstrating how to use MatchGo:

package main

import (
    "fmt"
    "github.com/Ravikisha/matchgo"
)

func main() {
    pattern, err := matchgo.Compile("([a-z]+) ([0-9]+)")
    if err != nil {
        fmt.Println("Error compiling pattern:", err)
        return
    }

    result := pattern.Test("hello 123")
    if result.Matches {
        fmt.Println("Match found:", result.Groups)
    }
}

This code will output:

Match found: map[0:hello 123 1:hello 2:123]

Development Insights

Developing MatchGo involved significant research and implementation of various regex principles. Here are some of the critical aspects of the engine:

1. NFA Implementation: The engine builds a non-deterministic finite automaton (NFA) from the regex patterns, enabling efficient matching.

2. Token Parsing: MatchGo parses the regex string into tokens, allowing for flexible matching strategies.

3. State Management: The engine maintains states for capturing groups and backreferences, enhancing its ability to handle complex regex patterns.

4. Extensibility: Although currently minimalistic, the engine is designed with extensibility in mind, allowing for future enhancements and additional features.

Resources and References

Throughout the development of MatchGo, I referred to various resources, including:

• Implementing a Regex Engine
• Thompson’s Construction - Wikipedia
• Go by Example
• Regex101

These resources provided invaluable insights and helped refine the implementation.

Conclusion

MatchGo is an exciting step into the world of regex engines, offering a simple yet functional tool for developers looking to integrate regex capabilities into their Go applications. As this project evolves, I look forward to enhancing its features and refining its performance.

Feel free to check out the GitHub repository for more information, contribute, or experiment with the engine in your own projects. Happy coding!

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