COM 1355 Assignment #2.
Assigned:  Thursday, 16 January 2003
Due:       Thursday, 30 January 2003, by 1pm EST

Implement an attribute evaluator for quirk20 as specified below.
This phase shall consist of a Java package named attributes that
defines a public class named Attributes, which defines a
public static method

    public static void evaluator (qast.Ast pgm);

The evaluator operation takes as its argument the abstract syntax
tree for a complete and error-free quirk20 program, and records
the D.sleaf, D.dleaf, and E.tail attributes as follows:

    For each function declaration D, the evaluator operation
    uses Ast.update1 to record D.sleaf, and Ast.update2 to
    record D.dleaf, using the encoding described by the table
    below:

        value    encoding
        -----    --------
        true         1
        false        0

    For each procedure call expression E, the evaluator
    operation uses Ast.update1 to record E.tail using the
    encoding described by the table above.

The evaluator operation should have no side effects apart
from those listed above.

The instructor is providing Java code to parse a quirk20
program and to implement the Qtype abstract data type.
See the documentation on the web page.  The code is in

    /course/com1355/Assignments/Assignment2

Please do not modify the instructor's code, as that would
make it harder to combine your semantic analysis phase with a
code generator written by someone else.  If you find a bug in
the instructor's code, please report it.

Submit this assignment using the submit-1355 script that is
documented on the course web page.