Note 2, DM546, fall 2019

Lecture February 8

• Syntax analysis (parsing).

Exercises February 12

• Appel 2.1 a-f.
• Discuss the C programming style introduced in Appel, Chapter 1. Make changes in Program 1.5 corresponding to the addition of the following rules to Grammar 1.3:
  • Exp → string
  • Exp → sqrt ( Exp )
  • Stm → if ( Exp ) then Stm
• Read about Flex. Make an overview of the additional possibilities for specifying regular expressions which are available in the tool compared with what was discussed at the lecture.
• What does the following regular expressions match?
  • \"([^\"])*\"
  • http:[^?]*\?
  • [-+]?[0-9]*\.[0-9]+([eE][-+]?[0-9]+)?
• Make and test the following three Flex scanners:
  • Make texts politically correct. Replace "idiot" with "intellectually challenged person", etc.
  • Remove all whitespace and produce lines in lengths of 80 characters.
  • Remove all tags from an HTML document. For those who do not speak HTML fluently, HTML is just regular text with some extra interpreted constructions. A "tag" consists of a "less than" symbol followed by some text and closed by a "greater than" symbol (you can view the source of this page to see an example).