Tools

Lex (or Flex)

• Purpose: Lexical analysis

• It reads raw input text and converts it into tokens (identifiers, keywords, numbers, symbols, etc.).

• You describe token patterns using regular expressions.

• Output: a scanner function (usually yylex ) that returns tokens to the parser.

• Example tasks:

  • Recognize keywords like if, while

  • Identify numbers, strings, operators

  • Skip whitespace and comments

Yacc (or Bison)

• Purpose: Syntax analysis

• It takes tokens from Lex and checks whether they follow the grammar of the language.

• You describe the grammar using context-free grammar rules.

• It builds a parse tree or triggers semantic actions.

• Example tasks:

  • Enforce operator precedence

  • Validate expression structure

  • Drive AST construction or code generation