CSE 3341, Core Interpreter Project, Part 2 (Parser, Printer, Executor)
Due: 11:59 pm, Friday, Nov. 10, ’23; 100 points
Notes:
1. This is the second part of the Core interpreter project. In this part, you have to implement the parser,
printer, and executor. You should use the same language, Java or Python, that you used for writing
your Tokenizer.
2. If there are any special considerations for compiling and running your code, make sure you specify,
in your README file, how your code is supposed to be compiled and run.
3. Your interpreter should take two command-line arguments. The first will be the name of the file that
contains the Core program to be interpreted. The second will be the name of the file that contains the
data for the Core program. Note that this is a change from the Tokenizer project. In that project, your
Tokenizer read the input Core program from the standard input stream. But now, since there are two
input files, the names of these files will be given as command-line arguments.
4. The Core program in the first file will not contain any illegal tokens but may contain other kinds
of errors, i.e., not meeting the requirements of the BNF grammar of Core; undeclared variables;
uninitialized variables; and another kind of error described in the next item. If the Core program
violates the BNF grammar or if undeclared variables are used in the <stmt seq> portion of the
Core program, your interpreter, before execution begins, should print an appropriate error message
and stop.
5. The data in the second file will consist of a sequence of integers (positive or negative), one per line.
This data will be read when your interpreter executes the “read” statements in the Core program.
If this file is empty when the interpreter tries to execute a “read” statement, your interpreter should
terminate with a suitable error message.
6. If during execution, the interpreter tries to access the current value of an identifier which has not yet
been initialized, your interpreter should terminate with a suitable error message.
7. The output from your interpreter should go to the standard output stream.
8. If there are no errors related to the requirements of the BNF grammar and no undeclared variables
appear in the <stmt seq>, the print-procedures of your interpreter should pretty-print the Core
program and then execute the program.
9. Pretty-printing requirements: There are no specific requirements about what precisely “pretty-printing”
means. Follow your own instincts on what would make the structure of any given program easy to understand and try to implement that. The goal is to make the structure of the code clear by just looking
at the pretty-printed version. Python’s indenting style is a good model to follow. Our eyes/brain seem
naturally wired to group together lines that are aligned (vertically) with each other. So, the Python
model is a good one to follow; or come up with your own variation – as long as it makes the code
clear by looking at it. (This site seems to do a reasonably good job of describing best pravctices in
Python regarding formatting: Python best practices
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10. During execution, if your interpreter executes an <out> statement such as “write X, Y;”, and
the values of X and Y at that point are 20 and 30, your interpreter should produce the following output:
X = 20
Y = 30
11. Important: Your code must follow the principles of encapsulation (also known as “abstraction”) that
we have talked about, rather than have the details of the representation of the abstract parse tree visible
to all parts of your interpreter. In other words, do not use the PT[] explicitly in your parse, print and
execute methods. Instead, use either the ParseTree class approach or the approach using a separate
class corresponding to each non-terminal in the grammar. If you violate this guideline, your lab will
be penalized heavily even if it is otherwise correct.
12. Zip all your files into one archive and submit to Carmen. (If Carmen doesn’t accept the Zip file,
upload to your “My Files” site on Carmen and submit from there.)
What To Submit And When: On or before 11:59 pm on the due date, you should submit, on Carmen, the
.zip file as specified above. DO NOT include object files in your .zip file. If the grader has problems with
compiling or executing your program, he will e-mail you; you must respond within 48 hours to resolve the
problem. If you do not, the grader will assume that your program does not, in fact, compile/execute properly.
The project will be graded using the project rubric on Piazza.
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