COSC 152 Programming Languages
Fall 2006
Homework Assignment #11
Objects
Due: Friday, Dec 08, 2:00PM CST
Submit: E-mail electronic
copy to professor, with a subject header "COSC 152 HW#11".
Work may be completed in groups of up to three students. Each group
should submit only once. Be certain to put all team member names on
work submitted. It would be courteous to carbon-copy your team mates
when e-mailing the final submission.
This assignment is largely the grammar from HW
#8, plus forms similar to Figure 5.7 on page 180 in EoPL.
The total grammar, in summary, should be:
| <program> |
::= |
{ <class-decl> }*
<statement> |
| <class-decl> |
::= |
class <identifier> extends <
identifier> {
{ field <identifier> ; }*
{ <method-decl> }*
} |
| <method-decl> |
::= |
method <identifier> (
{ <identifier> }*(,)
) {
{ <statement> ; }*
return <expression
> ; } |
| <statement> |
::= |
<identifier> = <
expression> |
| |
| |
print <expression> |
| |
| |
{{<statement>}*(;)
} |
| |
| |
if <expression> <
statement> else <statement> |
| |
| |
while <expression> <statement> |
| |
| |
var <identifier> = <expression>
; <statement> |
| <expr> |
::= |
<number> |
| |
| |
<identifier> |
| |
| |
<boolean> |
| |
| |
new <identifier> (
{ <expression> }*(,)
) |
| |
| |
send <expression> . <
identifier> (
{ <expression> }*(,)
) |
| |
| |
super . <
identifier> (
{ <expression> }*(,)
) |
| |
| |
( lambda ( {<symbol>}* )
<expr> ) |
| |
| |
( if <expr> <expr>
<expr> ) |
| |
| |
( cond { ( <bool-expr> <expr> )
}* ( else <expr> ) ) |
| |
| |
( let ( { ( <id> <expr> ) }*
) <expr> ) |
| |
| |
( letrec ( { ( <id>
( lambda ( { <id> }* ) <expr> ) }* )
<expr> ) |
| |
| |
( <expression>
{ <expression>}* ) |
With primitive operators add, sub, mul, div, mod, cons, car, cdr, list, empty-list, empty?, equal, lesser, greater, and, or, xor.
Modify your existing parse and execute functions
to handle programs in the new language.
Notes:
We will not be implementing type checking for this language, although
I encourage you to consider what it would entail (EoPL Ch 6.)
Most of the code required for this project is outlined in section
5.4.1 of EoPL, the "Simple Implementation".
All of your existing testcases from previous phases of the interpreter
should work in this new interpreter, with the exception of the
statements "proc" and "call", which have been removed
for simplicity.
Examples of object-oriented test cases are given throughout EoPL
Chapter 5, and all of these should work with only slight modifications.
(Our langauge has a little more of a Java feel to it.)
As an example, Figure 5.2 (EoPL p. 173) looks like
this in our variant.
The behavior of our language is as described in the text. We are
implementing single-inheritance, single dynamic dispatch, subclass
polymorphism. Methods can be overridden in child classes, and fields
are to be shadowed.
The top of the inheritance chain is a default class, "object",
methods bodies have an object pointer "self" in scope, and all
classes are assumed to implement a method "initialize" that
is called when new objects are allocated. Our grammar enforces that all
methods end with a return statement, so any method without
a meaningful return value should simply return a dummy expression, like
0.
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