4. Lex program that distinguishes keywords, integers, floats, identifiers, operators, and comments

 

Lex program that distinguishes keywords, integers, floats, identifiers, operators, and comments

/*Lex program that distinguishes keywords, integers, floats, identifiers, operators, and
comments in any simple programming language.*/ 
 
%{
enum{INTEGER,FLOAT,IDENTIFIER,OPERATOR,COMMENT};
%}
digit [0-9]
letter[A-Za-z_]

%%
" "|"\t" ;
{digit}+   { return INTEGER; }
{digit}+\.{digit}+ { return FLOAT; }
'+' |
'-' |
'*' |
'/' { return OPERATOR; }

{letter}({letter}|{digit})* { return IDENTIFIER; }
"/*" { return COMMENT;}
%%
int main(void)
{
  int result;
  int running = 1;
 while(running)
 {
  result = yylex();
  switch(result)
                {
  case INTEGER: printf("integer"); break;
  case FLOAT: printf("float"); break;
  case OPERATOR: printf("operator"); break;
  case IDENTIFIER:printf("identifier"); break;
  case COMMENT: printf("comment"); break;
  }
 }
return 0;
}
 
// Output of the above Program
Lex program that distinguishes keywords, integers, floats, identifiers, operators, and comments
Lex program that distinguishes keywords, integers, floats, identifiers, operators, and comments

Comments

Post a Comment

Popular posts from this blog

Compiler Design

CS 5641:  Fall 2009 Lecturer:  Rich Maclin  (rmaclin) Teaching Assistant: Bharat Siginam Syllabus Grades Useful software: gdb flex bison JavaCC NetBeans Eclipse Class Materials (previous offerings) Introduction Parts of a Compiler, Types of Programming Languages Lexical Analysis Introduction, Finite State Machines Regular Expressions, NFSMs, DFSMs, Translation Scanner Implementation     Sample code (gziped tar file) Parsing Introduction, Context Free Grammars, Languages, Derivations Ambiguity, Precedence, Associativity Top Down Parsing, Recursive Descent, Predictive Parsing, LL(1), First and Follow sets Bottom Up Parsing, Shift and Reduce, Conflicts SLR Parsing, SLR States     (PDF, 6 Per Page) Constructing SLR States, LR(1) Parsing, LALR Parsing Semantic Analysis Syntax-Directed Translation, Parse Trees, Abstract Syntax Trees Implementation Example with Bison, LL(1) Grammar     Co...
Read more

7. Lex specification program that generates a C program which takes a string “abcd” and prints the pattern

Image
  Lex specification program that generates a C program which takes a string “abcd” and prints the pattern /* Write a Lex specification program that generates a C program which takes a string “abcd” and prints the following output. abcd abc ab a */ % { # include < stdio.h > char ch; char i,j; % } %% [a - z] * { for (i = 'd' ;i >= 1 ; -- i) { for (j = 'a' ;j <= i; ++ j) { printf( "%c " ,j); } printf( " \n " ); } } %% int main() { yylex(); return 0 ; } //Output of the above program Lex specification program that generates a C program which takes a string “abcd” and prints the pattern
Read more

10. Program in YACC to recognize the string „abbb^n, „ab^n „a^n of the langauge (a^n b^n , n>=1)

Image
  Program in YACC to recognize the string „abbb^n, „ab^n „a^n of the langauge (a^n b^n , n>=1) //Program in YACC to recognize the string „abbb^n, „ab^n „a^n of the langauge (a^n b^n , n>=1) File Name : pr11.y %{ # include<stdio.h> int yylex ( void ); int yyerror ( char *); %} %token A B %% statement : expr ; expr :A expr B | A B ; %% int main () { printf( "Enter the string :" ); yyparse(); return 0 ; } int yyerror ( char *s) { printf( "Invalid" ); } File Name : pr11.l %{ # include "y.tab.h" extern int yylval; %} A [a] B [b] %% {A} {yylval=yytext[ 0 ]; return A;} {B} {yylval=yytext[ 1 ]; return B;} \ n { return 0 ;} . { return yytext[ 0 ];} %% // Output of the Above Program. Program in YACC to recognize the string „abbb^n, „ab^n „a^n of the langauge (a^n b^n , n>=1)
Read more