COMP 304B Object-Oriented Software Design - Assignment 3
  Due date: Sunday March 23, 2003 before 23:55

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Practical information

• Team size == 2 (pair design) !
• Each team submits only one full solution. Use the index.html template provided on the assignments page. Use exactly this format to specify names and IDs of the team members. The other team member must submit a single index.html file containing only the coordinates of both team members. This will allow us to put in grades for both team members in WebCT. Beware: after the submission deadline there is no way of adding the other team member's index.html file and thus no way of entering a grade !
• Your submission must be in the form of a simple HTML file (index.html) with explicit references to all submitted files as well as inline inclusion of images. See the general assignments page for an index.html template.
• The submission medium is WebCT.

Goal

In this assignment you will use UML State Machines to specify whether to accept or reject a series of input characters from an input character stream. The specification will be derived by you from a Regular Expression specification. The automaton will not only accept/reject input, but will also determine pertinent properties (such as value) of the recognized token. For the spreadsheet application, we need to be able to recognize Number and CellRef tokens. You will encodecode both automata in the given Python framework and run the simple provided tests.

Your assignment solution should contain:

1. A state automaton completely specifying recognition of

   • A spreadsheet Number. A Number is specified as follows:

       D             [0-9]
       E             [eE][+-]?({D})+
       Number        [({D}+{E}?)
                      ({D}*'.'{D}+({E})?)
                      ({D}+'.'{D}*({E})?)]
          
     

     Note how this specification is taken from the ANSI C grammar, Lex specification.

     D and E are macros which are expanded literally wherever {D} and {E} occur. Wherever no ambiguity exists, characters such as 0 stand for themselves '0'. [] denotes or. * denotes 0 or more times repeated. + denotes 1 or more times repeated. ? denotes exactly 0 or 1 occurrences. Brackets () allow for grouping.

     The automaton should set self.value and self.exp attributes to hold the mantissa and exponent respectively.

   • A spreadsheet CellRef. A CellRef is specified as follows:

       '$'?[a-zA-Z][a-zA-Z]?'$'?[1-9][0-9]?[0-9]?[0-9]?
          
     

     The automaton should set self.row, self.rowIsAbsolute, self.column and self.columnIsAbsolute attributes to hold appropriate integer values.

   You may use any drawing tool to produce the automaton.

2. An encoding, in the file scanner.py, of both patterns in the form of the classes NumberScanner and CellRefScanner, derived from the Scanner class given below.
3. The results of the simple tests in tests.py.

Upload all files to WebCT and provide links to them from your index.html file.

Starting Point and Example

The Regular Expression [10]*0 is recognized by the automaton below.

The scanner is encoded in the class EvenBinaryScanner in scanner_evenBinary.py. This requires an input stream class CharacterStream found in charstream.py. The test script test_evenBinary.py produces the following output when the __trace__ variable is set to False. It produces the following output when the __trace__ variable is set to True.