scanner.h

#ifndef clox_scanner_h
#define clox_scanner_h

// In clox the scanner produces a synthetic "error" token for an error
// and passes it over to the compiler. This way, the compiler knows an
// error occured and can kick off error recovery before reporting it.
typedef enum {
  // Single-character tokens.
  TOKEN_LEFT_PAREN, TOKEN_RIGHT_PAREN,
  TOKEN_LEFT_BRACE, TOKEN_RIGHT_BRACE,
  TOKEN_COMMA, TOKEN_DOT, TOKEN_MINUS, TOKEN_PLUS,
  TOKEN_SEMICOLON, TOKEN_SLASH, TOKEN_STAR,
  // One or two character tokens.
  TOKEN_BANG, TOKEN_BANG_EQUAL,
  TOKEN_EQUAL, TOKEN_EQUAL_EQUAL,
  TOKEN_GREATER, TOKEN_GREATER_EQUAL,
  TOKEN_LESS, TOKEN_LESS_EQUAL,
  // Literals.
  TOKEN_IDENTIFIER, TOKEN_STRING, TOKEN_NUMBER,
  // Keywords.
  TOKEN_AND, TOKEN_CLASS, TOKEN_ELSE, TOKEN_FALSE,
  TOKEN_FOR, TOKEN_FUN, TOKEN_IF, TOKEN_NIL, TOKEN_OR,
  TOKEN_PRINT, TOKEN_RETURN, TOKEN_SUPER, TOKEN_THIS,
  TOKEN_TRUE, TOKEN_VAR, TOKEN_WHILE,

  TOKEN_ERROR, TOKEN_EOF
} TokenType;

// We use the original source string as our character store. We represent
// a lexeme by a pointer to its first character and the number of characters 
// it contains. This means we don't need to worry about managing memory for 
// lexemes at all and we can freely copy tokens around. As long as the main
// source code string outlives all of the tokens, everytying works fine.
typedef struct {
    TokenType type;
    const char* start;
    int length;
    int line;
} Token;

void initScanner(const char* source);
Token scanToken();

#endif