Project 2 Lexical analysis

Project2
Due: see class calendar
Goal:
This assignment serves several purposes:
• to be familiar with flex
• to understand lexical analysis using the existing tool
Description:
In this assignment, you are required to use flex – a scanner generator to generate a scanner for Tiger
language. The manual for Tiger language can be found at the class repository: Tiger\manual.pdf.
Tiger language:
The reserved words of the language are:
while, for, to, break, let, in, end, function, var, type, array, if, then, else, do, of, nil.
The punctuation symbols used in the language are:
, : ; ( ) [ ] { } . + - * / = < < <= = & | :=
The string value that you return for a string literal should have all the escape sequences translated into
their meanings.
There are no negative integer literals; return two separate tokens for -32.
Detect unclosed comments (at end of file) and unclosed strings.
Tips and Requirements:.
Your lexer should use regular expressions to do the work EXCEPT for the nesting counting. For
example, don’t find a beginning quote and then use C++ code to look for matching end quote… use
regular expression(s)….
The comments in Tiger language is the same as C style comments that start with /* and end with the
matching subsequent */. Any symbol is allowed within a comment. However, the comments can be
nested, i.e.,
/* this is a line
/* this is ok
As many lines as you desire
This one only has three
*/ this closes the nested comment
*/ // this closed the first one.
Nesting can be of any level. Comments are ignored similar to whitespace. To handle nested
comments, you will need a counter within lexer that counts the beginning of comment and decrements
when ending. The comment is completed when it reaches zero.
String literal is a sequence, between quotes (“), of zero or more printable characters, spaces, or escape
sequences. Each escape sequence is introduced by the escape character \, and stands for a character
sequence. The allowed escape sequences are as follows (all other uses of \ being illegal):
• \n a character interpreted by the system as end-of-line.• \t TAB
• \” the double-quote character (“)
• \\ the backslash character (\)
What to do in this project?
You need to provide rules to recognize reserved words (while, for, to, break, let, in, end, function,
var, type, array, if, then, else, do, of, nil), punctuation symbols (, : ; ( ) [ ] { } . + - * / =
< < <= = & | :=), comments, identifiers, integer literals, and string literals. More
specifically,
• For white space character like “ “, \n, and \t; recognize them and discard it.
• For each recognized reserved words , and punctuation symbols, return their corresponding
tokens in the rule action. All tokens are defined in tokens.h file.
• For comments, just ignore all content in the comments. Make sure your rules recognize nested
comments.
• For integer literal, recognize it and return the INT token. Make sure you store the associated
integer value to variable yylval.ival.
• For identifier, recognize it and return the ID token. Make sure you store the associated name to
variable yylval.sval.
• For string literal, it is better to use start condition
o For the double quote (“) marking the beginning of the string literal, reset the variable
value to be an empty string, modify variables beginLine and beginCol, and start
STRING condition;
o For all rules under STRING condition that recognize part of the string literal, append
the recognized part to the variable value;
o For all rules under STRING condition that finds an error (like illegal escape sequence,
unclosed string), report the error.
o For the closing double quote (“), copy variable value to yylval.sval, just like the actions
in identifier rule, and start the INITIAL condition.
Make sure the provided function newline() is called for every newline character in the source file.
Make sure the provided function error() is called for every recognized errors (illegal character,
unclosed comments/strings, illegal escape character sequences, etc.). Other than calling function
error(); there should be no output statement in rule actions.
Instructor provided files in the class repository
The following files are provided by the instructor:
• Folder FlexProject. This contains a sample Visual Studio 2010 project. If you want to use this
provided project for this assignment instead of creating your own project from scratch, please
pay attention to the following:
o You have installed the Flex and Bison as specified in the class repository document:
How-to\flex and bison\ flex and bison installation.doc
Make sure the folder (like c:\gnuWin32\bin) containing flex.exe/bison.exe is added to
your path.
o Make sure instructor provided FlexLexer.h and flex.skl are copied to the correct
location as specified in the first 2 pages of the following document in the class
repository:
How-to\flex and bison\windows\ HOWTO-C++-flex-bison-Visual Studio.doc
o Skeleton source files provided in the sample project are listed below: tokens.h: contains the definition of all tokens and definition of YYSTYPE,
which is a structure to hold values associated with matched token.
 ErrorMsg.h: contains the definition of error handler
 main.cpp: the driver
 tiger.ll: a flex skeleton file for this project. In this assignment, you only need to
work on this file. No change on other files is necessary.
 Test0.tig, test1.tig, test2.tig: different test program of tiger language
• Description2.pdf: this file
• Rubric2.doc: the rubric used to grade this assignment.
• Test0.txt, test1.txt, and text2.txt. These are instructor provided output for test0.tig, test1.tig,
and test2.tig, respectively. Your output may be different depending on how you handle string
errors.
HOW TO GET STARTED
1. Pull from class repository on ranger to your local class repository. All files provided by the
instructor can be found at projects/project2.
2. Create master repository on ranger as specified on “How to prepare for projects”….see class
repository.
3. Clone your project2 master repository on your local machine, and copy folder FlexProject to your
local repository of project2.
4. Add folder FLexProject to git, and commit, and push it to master repository.
5. After making significant progress, make sure you submit the change to local repository and push
all the changes to master repository on ranger.
6. Finish coding and debugging...remember to add comments and commit as needed.
7. Once you have finished, submit the project in the following way:
• Copy the file projects/project2/rubric2.doc from the class repository to the project2
folder in your local repository of project2. Edit the file to put your name.
• Commit the whole project2 folder to your local repository.
• Push all the changes to master repository on ranger.
• Any commit of the project after the deadline is considered as cheating. If this
happens, the latest version before the deadline will be graded, and you may
receive up to 50 points deduction.
8. You can check your grade by update the rubric2.doc from the repository after the notice from the
instructor.