Regular Expression Parser

Overview

This project implements a Regular Expression (Regex) Parser in the C programming language. The parser supports a comprehensive set of regex meta-characters, escape sequences, and various matching patterns to enable sophisticated string matching capabilities.

Features

Meta Characters

• Parentheses (): Grouping of expressions.
• Square Brackets []: Specifies a character class.
• Curly Braces {}: Specifies a quantifier.
• Caret ^: Indicates the start of a line.
• Dollar $: Indicates the end of a line.
• Dot .: Matches any character except a newline.
• Backslash \: Used for escaping meta-characters.

Escape Character

• Escape Character \: Used to escape meta-characters.

Character Classes

• Within Square Brackets [ ]: Specify a set of characters to match.

Quantifiers

• Question Mark ?: Matches zero or one occurrences of the preceding element.
• Asterisk *: Matches zero or more occurrences of the preceding element.
• Plus Sign +: Matches one or more occurrences of the preceding element.
• Curly Braces {}: Specify a specific number of occurrences or a range.

Alternation

• Vertical Bar |: Indicates alternation, allowing for multiple possible matches.

Examples

• hello contains {hello}
• gray|grey contains {gray, grey}
• gr(a|e)y contains {gray, grey}
• gr[ae]y contains {gray, grey}
• b[aeiou]bble contains {babble, bebble, bibble, bobble, bubble}
• [b-chm-pP]at|ot contains {bat, cat, hat, mat, nat, oat, pat, Pat, ot}
• [a-zA-Z] matches any lowercase or uppercase letter.
• colou?r contains {color, colour}
• rege(x(es)?|xps?) contains {regex, regexes, regexp, regexps}
• go*gle contains {ggle, gogle, google, gooogle, goooogle, ...}
• go+gle contains {gogle, google, gooogle, goooogle, ...}
• g(oog)+le contains {google, googoogle, googoogoogle, googoogoogoogle, ...}
• z{3} contains {zzz}
• z{3,6} contains {zzz, zzzz, zzzzz, zzzzzz}
• z{3,} contains {zzz, zzzz, zzzzz, ...}
• [Gg]o\*\*le contains {Go**le, go**le}
• \d matches any digit.
• 1\d{10} matches an 11-digit string starting with a 1.
• Hello\nworld contains Hello followed by a newline followed by world.
• mi.....ft contains a nine-character substring beginning with "mi" and ending with "ft".
• ^dog begins with "dog".
• dog$ ends with "dog".
• ^dog$ is exactly "dog".
• [^i*&2@] matches any character other than "i", "*", "&", "2", or "@".
• ([A-Z])\w+ finds all words starting with an uppercase letter.

Usage

1. Clone the repository.
2. Compile the source code using a C compiler.
3. Run the compiled executable with appropriate input strings to test the regex patterns.

Contribution

Contributions to improve and extend the functionality of this Regular Expression Parser are welcome. Please fork the repository, make your changes, and submit a pull request.

License

This project is licensed under the MIT License.