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.
This assignment will make you familiar with unit testing
and object-oriented programming in Python.
You will test and implement classes
to represent formulas used in spreadsheet cells. This is the
very first step towards a simple spreadsheet application.
For testing, you will use the unittest framework in
Python.
Your assignment should clearly present:
The tests corresponding to the requirements listed below.
An implementation of the design given below.
The results of the tests on your implementation.
Upload all source and result files to WebCT and provide
links to them from your index.html file.
Design
In Figure 1, the design for this assignment is
given in the form of a UML Class Diagram.
Figure 1: The spreadsheet cell formula node UML Class Diagram
You must test and implement all classes. The structure of the classes
is given in the design. You must adhere strictly to the given design.
Note how the design specifies describe the abstract class FNode
with its concrete realizations in the form of sub-classes.
The Operator class is linked to the FNode class denoting
the fact that an Operator node refers to its children.
Actually, the design already specifies that the reference to the
children will be through an attribute _children of
type List_Of_FNodes.
Although a Number can be instantiated with either an
Integer or a Float, internally, storage is as a Float.
Furthermore, you are required to perform all arithmetic on
Floats only. Using Integer arithmetic would complicate
matters when dealing with division.
A side-effect of using Floats is that 1/1/x is usually
not equal to x. This is due to the internal representation
of floating point numbers and errors made during calculations.
Hence, equality of two floating point numbers a and b
will have to be tested by checking whether |a-b| < e with
e a tolerance.
You will implement the evaluate() method for all classes
except CellRef. The latter will only be possible at the level of
the overall spreadsheet (in a later assignment).
Note how evaluate() does not return a Float, but
in true object-oriented fashion, returns an object, instance of the
Number class !
Requirements
1. Test for Success
Calling any concrete evaluate method must return an instance of
class Number.
Build some tree data structures containing instances of classes
Operator and Number (ignore class CellRef for now).
Make sure ``evaluating'' the root node returns the expected result.
For instance, if a is the
root node of a tree representing the operation 2+4-5,
make sure that a.evaluate.getValue() returns 1.
2. Test for Failure
FNode:
An attempt to instantiate this abstract class should raise
a NotImplementedError exception.
Operator:
An attempt to instantiate this abstract class should raise a
NotImplementedError exception.
Number:
Raise a TypeError if the argument passed
to the constructor is
not of the right type (Integer or Float).
CellRef:
Raise a TypeError if the arguments passed to
the constructor
are not of the right type
(row and column are Integers,
isRelative is a String).
Check that refKind is either "RELATIVE" or ÄBSOLUTE".
If not, raise a ValueError.
If isRelative equals ÄBSOLUTE", make sure that row and
column are both non-negative. If not, raise a ValueError.
Sum and Product:
Check that the parameter children is a
List. If not, raise a TypeError.
Check that the list contains at least two items. If not, raise a
TypeError.
Check that each item of that list is an instance (direct or not) of class
FNode. If not, raise a ValueError.
InverseSum and InverseProduct:
Check that the argument child
is a List. If not, raise a TypeError.
Check that the list contains a single item. If not, raise a
TypeError.
Check that the single item is an instance (direct or not) of class
FNode. If not, raise a ValueError.
3. Test for Sanity
Do some sanity checks with classes InverseSum and
InverseProduct. That is (for instance),
x + (-x)
=
0,
- (-x)
=
x.
Make sure the value returned by Number.getValue is consistent
with the value stored in the attribute Number.__value.
Make sure the method Number.evaluate returns the caller object
itself (use Python's is operator as in a is b).
