09CS303 Laboratory

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PES-INSTITUTE OF TECHNOLOGY

DHEERAJ.D

Asst.Prof

Dept. of ISE, PESIT

09 CS 303

Compiler Design-Laboratory Manual.For 5th Semester students.

By

(Autonomous Institute under VTU , Belgaum and UGC , New Delhi)100 feet ring road, BSK 3rd stage,

Banglore-560 085.Phone: 080-2672 1983, Fax: 080-2672 0886. http://pesit.pes.edu


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Compiler Design-Laboratory Manual.

Dept of IS&E, PESIT

Lex and Yacc

1. Write a lex Program to identify a simple and a compound statement.%{

#include

int F0=0,F1=0,F2=0,error=0,l1=0,l2=0;

%}

verb am|run|sit|did|study|is|large|go|come

subject [a-zA-Z]+

compnd and|but|also|either|neither|yet|still|consequences

%%

{verb} { if(F2==1)

l2=1;

F2=1;

if(F1==0)

error=1;

}

{compnd} { F0=1; }

{subject} { if(F1!=0)

l1=1;

F1++;

}

%%

main()


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{

printf(\n Enter a sentence: );

yylex();

if(error==1 || F2==0 || F1==0)

{

printf(\n Invalid sentence);

exit(0);

}

if(F0==1 && l1==1 && l2==1)

printf(\n Compound sentence\n);

else

printf( \nSimple sentence\n);

}

Aliter

%{#include

int flag=0;

%}%%

if|

because|or|

either|nor|

neither|but{flag=1;}}%%

main()

{printf("Enter the sentence");

yylex();

if(flag)


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{

printf("compound");

elseprintf("simple");

}

}2. Write a lex Program to count the number of keywords and identifiers in a sentence.%{

#includestatic int key_word=0;

static int identifier=0;

%}

%%"include"|"for"|"define" {key_word++;printf("keyword found");}

"int"|"char"|"float"|"double" {identifier++;printf("identifier found");}

%%int main()

{

printf("enter the sentence");

yylex();printf("keyword are: %d\n and identifier are: %d\n",key_word,identifier);

}

3. Write a lex program to convert an octal number to decimal number.%{

#include

Void octtodeci(int);

%}

%%

[0-7]+{octtodeci(atoi(yytext));}

%%

int main()

{

Printf(\n enter the octal number);

Yylex();

}

Void octtodeci(int num)

{


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Dept of IS&E, PESIT

int sum=0;

int r=0;

int i=0;

while(num!=0)

{

r=num%10;

sum=sum+r*po(8,i);

i++;

num=num/10;

}

Printf(\n the decimal equivalent is %d,sum);

}

int po(int a , int m){

int j=0;

int k=1;

for(j=0;j


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Dept of IS&E, PESIT

%%

yyerror()

{

Printf(\n the string does not belong to the grammar);

}

int yylex()

{

char ch;

ch=getchar();

if (ch==a)

return A;

else if (ch==b)

return B;else if(ch==\n)

return 0;

else return ch;

}

int main()

{

Printf(enter the expression \n);

yyparse();

Printf(\n string accepted by grammar);Return 0;

}

5. Write a YACC program to check the validity of an arithmetic expression.

%{

#include

#include

%}%token ID

%left '+','-'

%left '*','/'

%%

E:E'+'E { printf("valid expression);}| E'-'E { printf("valid expression);}


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| E'/'E { printf("valid expression);}

| E'*'E { printf("valid expression);}

| ID;

%%

int yylex(){Char ch;

Ch=getchar();

if(isalnum(ch))return ID;

else if(ch==\n)

return 0;

else return ch;

}

yyerror()

{

Printf(\n invalid expression);

}

int main()

{

printf("Enter the expression");yyparse();

}

6. Write a YACC Program to identify an input for the grammar a^nb (n>=10)

/* 6.l lex part*/

%{

#include

#include y.tab.h


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%}

%%

[aA] return A;

[bB] return B;

.|\n return yytext[0];

%%

6.y

/* 6.y yacc part */

%{

#include

%}

%token A B

%%

stmt: S \n {printf(\nValid expression); exit(1);}

;

S: X B

X: X A | AAAAAAAAAA

%%

main()

{

printf(\nEnter the expression: );


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Dept of IS&E, PESIT

if(yyparse())

{

printf(\nValid expression);

exit(0);

}

}

int yyerror()

{

printf(\nInvalid expression\n);

return 1;

}

int yywrap()

{

return 1;

}


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ANTLR(Another tool for Language Recognition).

In computer-based language recognition, ANTLR (pronounced Antler), or Another Tool for

Language Recognition, is a parser generator that uses LL (*) parsing. ANTLR is the successor to

the Purdue Compiler Construction Tool Set (PCCTS), first developed in 1989, and is under

active development. Its maintainer is Professor Terence Parr of the University of San Francisco.

ANTLR takes as input a grammar that specifies a language and generates as output source code

for a recognizer for that language. At the moment, ANTLR supports generating code in the

programming languages Ada95, Action Script, C, C#, Java, JavaScript, Objective-C, Perl,

Python, and Ruby. A language is specified using a context-free grammar which is expressed

using Extended Backus Naur Form EBNF.

ANTLR allows generating parsers, lexers, tree parsers, and combined lexer-parsers. Parsers can

automatically generate abstract syntax trees which can be further processed with tree parsers.

ANTLR provides a single consistent notation for specifying lexers, parsers, and tree parsers. Thisis in contrast with other parser/lexer generators and adds greatly to the tool's ease of use.

By default, ANTLR reads a grammar and generates a recognizer for the language defined by the

grammar (i.e. a program that reads an input stream and generates an error if the input stream

does not conform to the syntax specified by the grammar). If there are no syntax errors, then the

default action is to simply exit without printing any message. In order to do something useful

with the language, actions can be attached to grammar elements in the grammar. These actions

are written in the programming language in which the recognizer is being generated. When the

recognizer is being generated, the actions are embedded in the source code of the recognizer at

the appropriate points. Actions can be used to build and check symbol tables and to emitinstructions in a target language, in the case of a compiler.

As well as lexers and parsers, ANTLR can be used to generate tree parsers. These are

recognizers that process abstract syntax trees which can be automatically generated by parsers.

These tree parsers are unique to ANTLR and greatly simplify the processing of abstract syntax

trees.


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Dept of IS&E, PESIT

How to install and use ANTLR?

Download ANTLR 3.2, eclipse, JDK 1.6. Open eclipse ide.

Select File

New

JPA Project. Enter container name, project name, ok or finish. Select FileNewjava project. Enter a project nameok. If there is a prompt that asks for build nature press ok. Right click on the project in the package explorer. NewotherANTLRcombined grammarnextenter grammar name (grammar

name = class name)ok.

The ide generates a .g file for you. Type the program in the text editor. Right click on the project in the package explorer. SelectconfigureANTLR project. Right click on the project again in the package explorer. Select Build pathadd external archives. Select the directory where the ANTLR jar file resides. Note: if there are no errors in your program, ANTLR generates a lexer and a parser file

for you.

Go to the interpreter, give the input for the grammar, ANTLR generates a parse tree asoutput.

If build fails, go to runrun asjava applicationokSelect Tool-org.antlrok, thisshould run your code.


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1. Write an ANTLr grammar to accept the pascal statement READ(Value) and print aparse tree for the same.

grammar Read;

options {language = Java;

}

tokens{READ = 'READ';

OB = '(';

CB = ')';

CM = ',';

}

@members{

/*public static void main (String [] args) throws Exception

{ReadLexer lex = new ReadLexer(new ANTLRFileStream(args[0]));

CommonTokenStream tokens = new CommonTokenStream(lex);

ReadParser parser = new ReadParser(tokens);

try{

parser.expr();

}catch(RecognitionException e)

{

e.printStackTrace();}

}*/

}

IDLIST : ID(((CM)ID)+)?;

fragment ID : AL+;

fragment AL : 'a'..'z'|'A'..'Z';

read: READ OB IDLIST CB;


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2. Write an ANTLr grammar to perform basic arithmetic operation in a calculatorgrammar Test;

options {

language = Java;

}

tokens{PLUS = '+';

MINUS = '-';MULT = '*';

DIV = '/';

ASSIGNMENT =':=';

}@members

{

public static void main(String[] args)

throws Exception{

TestLexer lex = new TestCalLexer(new ANTLRFileStream(args[0]));

CommonTokenStream tokens = new CommonTokenStream(lex);TestParser parser = new TestParser(tokens);

try

{

parser.expr();}

catch(RecognitionException e)

{e.printStackTrace();

}

}}

/*Lexer Rules*/

ID: A+;NUMBER: (DIGIT) + ('.' (DIGIT)+)? ;

WS: ('\t'|' '|'\r'|'\n')+ ;

fragment A : 'a'..'z'|'A'..'Z';/*fragment:Special construct in ANTLR to describe a part of another rule*/fragment DIGIT: '0'..'9' ;

/*Parser Rules*/

stmt: ID ASSIGNMENT expr;expr:term((PLUS|MINUS)term)*;

term:factor((MULT|DIV)factor)*;

factor: ID | NUMBER;


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3. Write an ANTLr grammar to accept a block of PASCAL statements between beginand end and print the parse tree for the same.

grammar Prog1;

options {language = Java;

}

tokens{

ASSIGN = ':=';

PLUS = '+';

MINUS = '-';MULT = '*';

DIV = '/';

TO = 'TO';DO = 'DO';

BEGIN = 'BEGIN';

END = 'END';

WRITE = 'WRITE';SEMICLN = ';';

FOR = 'FOR';

OB = '(';CB = ')';

CM = ',';

}

ID: A+;

NUMBER : (DIGIT)+('.' (DIGIT)+)? ;//WS: ('\t'|' '|'\r'|'\n')+ ;

fragment A : 'a'..'z'|'A'..'Z';

fragment DIGIT: '0'..'9';for: FOR ID ASSIGN NUMBER TO NUMBER DO BEGIN stmtlist END;

stmtlist: stmt+;

stmt: write | ID ASSIGN expr SEMICLN;expr:term((PLUS|MINUS)term)* ;

term:factor((MULT|DIV)factor)*;

factor: ID | NUMBER;

write : WRITE OB idlist CB SEMICLN;idlist : ID((CM ID)+)?;


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4. Write an ANTLr grammar to decide whether given sentence is simple or compound.grammar Prog2;

options

{language = Java;

}

VERBS : 'doing' | 'using';

NOUN : 'bangalore' | 'dog';

ADJECTIVE : 'complicated'|'massive';

sentence : (VERBS|NOUN|ADJECTIVE)+;


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Dept of IS&E, PESIT

09 CS 303

Week # Program # List of Programs

1Instruction

class.

Introduction to the lab procedures and evaluation scheme, Lex and YACC

specifications.

2 Program #1 Write a lex Program to identify a simple and a compound statement.

3 Program #2 Write a lex Program to count the number of keywords and identifiers in a sentence.

4 Program #3 Write a lex program to convert an octal number to decimal number.

5 Program #4Write a YACC Program to check whether given string a^nb^n is accepted by the

grammar.

6 Program #5 Write a YACC program to check the validity of an arithmetic expression.

7 Program #6 Write a YACC Program to identify an input for the grammar a^nb (n>=10).

8Instruction

classInstruction class on ANTLR (Another tool for Language Recognition).

9 Program #1Write an ANTLr grammar to accept the pascal statement READ(Value) and print a

parse tree for the same.

10 Program #2 Write an ANTLr grammar to perform basic arithmetic operation in a calculator

11 Program #3 Write an ANTLr grammar to accept a block of PASCAL statements between begin andend and print the parse tree for the same.

12 Program #4 Write an ANTLr grammar to decide whether given sentence is simple or compound.


09CS303 Laboratory

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