Hints for exercise 2

General hints about regular expressions:

• Choice: | and [ ] and [^] and .
• Start and end of line: ^ and $
• Repetition: * and +
• Building up arbitrarily complicated regular expressions: ( )
• Using special characters to just mean themselves: \ " and [^-] inside [ ]

Specific problems you might encounter:

• I don't understand the error messages I'm getting from flex (or gcc):
  • "warning, rule cannot be matched"
  • "EOF encountered inside an action"
  • loads of wierd error messages like these
• I've got a rule that should recognise keywords, but it isn't working: put special cases before more general rules
• I want to recognise a "+" (or "*" or "[" etc.) but lex is treating it as a special character instead: outside [ ] and inside [ ]
• I want to recognise complex patterns like strings, comments and preprocessor commands