The lab4 repo initially contains starter lex/yacc files for lab4
(details on the lab are at url csci.viu.ca/~wesselsd/courses/csci330/labs/lab4/)

This includes a makefile to build the lab4x parser,
   initial versions the lab4.lex and lab4.yacc files,
   a subdirectory for valid yarrgh test cases, and
   a subdirectory for invalid (broken) test cases.

What the starter lab4 lex/yacc files actually recognize is just a portion of the desired
        yarrgh programming language.

    The currently supported form of a program is
        open
           one or more statements
        close

    where the supported statement types are
        integer variable declarations of the form
            def identifier integer ;
        assignment statements of the form
            set identifier expression ;
    where expressions can be identitifers, integer literals, or
         summations of identifiers and integer literals.

    The supported token types are:
       identifiers, which consist of one or more lowercase alphabetic letters
       integer literals, which consist of one or more digits

    Comments are supported as everything on a line from a # symbol to the end of the line
       (where comments can begin anywhere on a line).