CS4121 Cminus Expression Interpreter Project

CS4121 Cminus Expression Interpreter Project

Purpose
The purpose of this project is to gain experience in giving meaning to a programming language by interpreting a subset of Cminus. Specifically, you will interpret integer and string write operations, integer read
operations, integer arithmetic and logical expressions and assignment statements.
Project Summary
In this project, you will add actions to a parser and a scanner provided by me. You must add code to do
the following:
1. Design a data structure to store string constants and integer variables declared in a Cminus program
and to track variable values.
2. Pass attributes of tokens from the scanner to the parser when needed.
3. Interpret string write statements.
4. Interpret integer write statements.
5. Interpret integer read statements.
6. Interpret integer expressions.
7. Interpret logic expressions.
8. Interpret assignment statements which assigns values to integer variables.
Requirements
Write all of your code in C or C++ . It will be tested on a Rekhi CS lab machine and MUST work there.
You will receive no special consideration for programs which “work” elsewhere, but not on a CS machine.
Input. The file CminusProject1.tgz contains the parser needed to begin this project. You will need to
modify the actions in the project files parser/CminusParser.y and parser/CminusScaner.l to do this
project. Currently, the actions in the parser just emit the rules that are reduced. You also need to set up
certain token attributes in the scanner. Sample input for this project is provided in the project directory
input. To run your interpreter, use the command
cmc <file.cm
You will see <file.s which contains the output of the Cminus program. Type in your input if the program
contains read statements.
Submission. Your code should be well-documented. You will submit all of your files, by tarring up your
project directory using the command
tar -czf CminusProject1.tgz CminusProject1
Submit the file CminusProject1.tgz via the CS4121 Canvas page. Make sure you do a ’make clean’ of your
directory before executing the tar command. This will remove all of the ’.o’ files and make your tar file much
smaller.
1
Data Structures and Documentation I have provided several C data structures for those who will
be programming in C. There are doubly linked list, symbol table and string manipulation routines in
the directory CminusProject1/util. The HTML Doxygen documentation for the provided code is in
CminusProject1/Documentation/html/index.html. You may ask me any questions regarding these routines. You will not likely need any of these structures now, but you may want to familiarize yourself with
them. For those coding in C++, you may use STL.
Makefile Structure The Makefiles for the project are set up to automatically generate make dependences.
In a particular directory (e.g., parser), you may add new files for compilation by adding the source file name
to the SRCS variable declaration on the first line of that directory’s Makefile. For example, to add the file
newfile.c to be compiled in the parser directory, change the first line of parser/Makefile from
SRCS = CminusScanner.c CminusParser.c
to
SRCS = CminusScanner.c CminusParser.c newfile.c
Nothing else needs to be done. Do not add source files to the root directory CminusProject1 as the make
files assume there are no source files in that directory.
If you would like to add your own subdirectory (e.g., newdir) to CminusProject1, then change the line
DIRS = parser util
in CminusProject1/Makefile to
DIRS = parser util newdir
and the line
LIBS = parser/libparser-g.a util/libutil-g.a
in CminusProject1/Makefile to
LIBS = parser/libparser-g.a util/libutil-g.a newdir/libnewdir-g.a
Then, copy util/Makefile to newdir/Makefile. Finally, change the SRCS declaration in newdir/Makefile
to contain only the source files in that directory and change the line
ARCHIVE = libutil$(ENV).a
to
ARCHIVE = libnewdir$(ENV).a
An Example
Given the following Cminus program (3.add.cm):
int main () {
int i,j,k,l;
write(10+20);
i=1; k=3; l=4;
j = i + k + l;
write(j);
}
your expected output in 3.add.s should be
30
8
2
Additional Notes (Please read!)
The lexeme of STRING token as it is includes the leading and ending double quotes. The actual content of
the string should not include the quotes.
In both CminusParser.y and CminusScanner.l, I have renamed the prefix yy to Cminus . You will need
to use Cminus instead of yy as the prefix for the common Bison and Flex functions and global variables.
For example, instead of using yylval, use Cminus lval.
The write statement should output a newline by default.