How a Lexer Turns Source Code into Tokens: A Compiler Pipeline Explained

The compiler pipeline transforms source code through several stages — starting with the lexer, which scans raw text and converts it into a structured stream of tagged tokens using regular expressions. A parser then consumes those tokens and builds an Abstract Syntax Tree (AST) that represents the grammatical structure of the code. Semantic analysis follows, checking for type errors, undeclared variables, and incorrect function calls that the parser alone cannot catch. Finally, the validated AST is translated into LLVM IR, a language-agnostic intermediate representation that LLVM optimizes and compiles down to machine code for various hardware targets.