Assignment 2: Scanner and Symbol Table

(Posted on 03/28, Due 04/11 9:59PM)

In this assignment, you are required to write a C-- scanner (The language C-- has been posted on the class website) using the Lex/Flex tool.
You are also required to use basic symbol table manipulation routines (lookup(), insertID() and printSymTab()) provided to handle all identifiers.
Tokens to be scanned by your scanner are all valid symbols that you would expect to see in a C-- program.
There are five classes of tokens to handle: 1. operators, 2. separators, 3. identifiers, 4. reserved words and 5. constants

(See the C-- specification for the 5 classes of tokens).

Comments are considered as white spaces, and should be stripped off.
However, in this assignment, you should define comments as a token.
The rules for token definitions can be derived from the description of the C-- language.
Although your scanner should be designed to work with your parser (as in assignment#3), in this assignment, your scanner only needs to handle the following jobs:

a) Print each comment captured by your token RE (regular expression).
b) Print the frequency of each identifier

---

An example program is shown below along with the results that your scanner supposes to print out.

=============program start===============

int main()
{
/* 1: this is * just a / sample */
int n;
int abc, def, main_1;
int a1;
float b1, z_123_x_45;
write("Enter a number");

/* 2: this is a 3-line
    comment
*/
n = read();
abc = n + 1;
def = abc * abc;
write(def); /* 3: this is /* the end ***/
}

=============program end===============

The output from your scanner looks like the following:

/* 1: this is * just a / sample */
/* 2: this is a 3-line
    comment
*/
/* 3: this is /* the end ***/

Frequency of identifiers:
a1          1
abc         4
b1          1
def         3
main        1
main_1      1
n           3
read        1
write       2
z_123_x_45  1

---

Note

1. It is required that the outputs be sorted. You could simply use the strcmp library function to do the sorting. In this assignment, the entire " (double quote) delimited string is treated as a single token i.e. a string constant. In the case of some unknown tokens, your scanner should issue an error message, and print out the unrecognized token, then exit.
2. You may assume the identifier names will not exceed 256 characters. However, the number of distinct identifiers should not be limited.
3. In the hw2 directory you may find the following files:

    src/lexer.l           the lex template code that you may start with
    src/symboltable.c     contains symbol table manipulation routines
    src/header.h          contains a sample symbol table structure
    src/Makefile
    test/                 a test directory containing some sample tests
    tar.sh                package script

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Submission requirements

1. DO NOT change the executable name (scanner).

2. Use the script file “tar.sh” to package your assignment into a single file. Then upload your packaged assignment to e3.

Usage: ./tar.sh source_directory studentID1_studentID2 (all student IDs in your team) version_number Example: ./tar.sh hw 12345_12346 ver1 Output: 12345_12346_ver1.tar.bz2 (submit this file)

3. We grade the assignments on the linux1 workstation. Before summiting your assignment, you should make sure your version works fine on linux1.

If you need to make changes to your submitted files, you may submit a new version before the deadline.