Lexical Analyzer for C

A lexical analyzer for the C language, written in C using regex.

File Structure

.
├── lexer.h     # Token types and function declarations
├── lexer.c     # Lexer implementation
├── main.c      # Entry point
└── input.txt   # Input file for testing

How to Compile and Run

make run

How It Works

The lexer reads the source file as a string and scans it character by character using a cursor pointer. For each position, it tries to match a list of regex rules in order — the first rule that matches at the current position produces a token. Comments are discarded. Whitespace and newlines are skipped while keeping track of line and column.

Each token is returned with its type, value, and position (line/column).

Tokens

Token	Examples
RESERVED_WORD	int, if, return, while
IDENTIFIER	main, x, printf
NUMBER	42, 3.14
STRING	"hello"
CHAR	'A'
ARITHMETIC_OPERATOR	+, -, *, /, ++, --
LOGIC_OPERATOR	==, !=, &&, ||, >=
SEPARATOR	(, ), {, }, ;
COMMENT	// ..., /* ... */