Comp 212 Homework 3
Part I due Monday, Feb. 11, 2002 10:00 AM -
Part II due Monday, Feb. 18, 2002, 10:00 AM
No late submission will be accepted.
Your task is to write algorithms on
AList (see source
code ) as visitors
as specified in the following problems. You are free to add any private
and protected methods to your visitor classes to support your public operations.
You are also free to write helper visitors to support your main visitors.
You are not allowed to check for the type of any object , such as using instanceof
or add a method to check for the type, to perform any task. The
visitors should be in the package OOscheme.visitor,
unless specified otherwise.
matching parentheses as in Scheme. For example, ToString for the list
containing 1, 2 ,3, should return (1 2 3),
and ToString for the empty list should
that contains the first n elements of the host. Here
0 <= n, and the case n
equals 0 corresponds to the empty list. Decide how
to pass n to FirstNElements yourself.
Each of the above problems should be done independently from each other.
A common problem in computing is to read in an arithmetic expression such as 3 * (4 + 5) and evaluate it. This can be done by first parsing it and create a corresponding "abstract syntax tree" (AST):
Once the AST is built, one can then traverse and evaluate it. We are not concern with the problem of parsing at this point in time. What we want to do in this exercise is to build an object model for the AST and then write visitors to interpret it. We shall restrict ourselves to arithmetic expressions containing integers, strings (representing variables), and binary operations such as addition and multiplication. To evaluate such an expression, we need to have an environment that matches each variable in the expression with an integer value. An environment can be viewed as a set of id/value pairs. The complete UML diagrams with full javadoc documentation of an AST, its visitors and environments are given here. Your assignment is to read the documentation of each the diagrams, figure out what it means and implement it. 70 points
The homework is to be submitted in two milestones.
Each is to be submitted via the turn-in script.
To turn in Part 1 to comp212: