Common Mechanisms of UML

<parser.l>

%{

#include<stdio.h>

#include "y.tab.h"

%}

%%

[0-9]+ {yylval.dval=atof(yytext);

return DIGIT;

}

\n|. return yytext[0];

%%

<parser.y>

%{

/*This YACC specification file generates the LALR parser for the program

considered in experiment 4.*/

#include<stdio.h>

%}

%union

{

double dval;

}

%token <dval> DIGIT

%type <dval> expr

%type <dval> term

%type <dval> factor

%%

line: expr '\n' {

printf("%g\n",$1);

}

;

expr: expr '+' term {$$=$1 + $3 ;}

| term

;

term: term '*' factor {$$=$1 * $3 ;}

| factor

;

factor: '(' expr ')' {$$=$2 ;}

| DIGIT

;

%%

int main()

{

yyparse();

}

yyerror(char *s)

{

printf("%s",s);

}

Output:

$lex parser.l

$yacc –d parser.y

$cc lex.yy.c y.tab.c –ll –lm

$./a.out

2+3

5.0000

CD LAB PROGRAMS:

A Program to Design Lexical Analyzer

Implement the Lexical Analyzer Using Lex Tool

Implementation of Predictive Parser

Design LALR Bottom up Parser

Convert The BNF rules into Yacc form and writecode to generate abstract syntax tree

A Program to Generate Machine Code