Week 2/37

Exercises on scanners and parsers

1. Implement and test flex based scanners that:
   • formats text in 80-column blocks, while removing multiple, leading, or trailing blanks;
   • removes all tags from an HTML document; and
   • introduces plausible spelling errors.
2. Read the flex documentation and discuss the full syntax for regular expressions.
3. What do the following regular expressions match?
   • \"([^\"])*\"
   • http:[^?]*?
   • [-+]?[0-9]*\.[0-9]+([eE][-+]?[0-9]+)?
4. Find out about "start conditions" in flex.