Vishnu 's Terminal Diary

To program LEX programs and yacc programs you need to install two packages in Ubuntu 1:Flex -to make the Lex program work 2.Bison -to make the yacc programs work To install,Open terminal and do the following...  1.To install Flex sudo apt-get upgrade sudo apt-get install flex 2.To install Lex sudo apt-get upgrade sudo apt-get install bison And its done ..!!!

Lex Program to find the Syntax of Scanf() Source Code:- 1:  %{   2:  #include<stdio.h> 3:  #include<ctype.h> 4:  int i=0,j=0; 5:  %} 6:  a "%d"|"%f"|"%c"|"%s" 7:  id [a-zA-Z][a-zA-Z0-9]* 8:  %% 9:  scanf\((\"({a}*|.*)*\"(,\&{id})*\))\; {for(i=0;i<yyleng;i++){if(yytext[i]=='%') 10:  j++; 11:  if(yytext[i]==',') 12:  j--; 13:  } 14:  if(j==0) 15:  printf("\ncorrect");   16:  else   17:  printf("incorrect"); 18:  } 19:  %% 20:  main() 21:  { yyin=fopen("file13.c","r"); 22:  yylex(); 23:  } 24:  int yywrap() 25:  {return 1; 26:  }      

Lex Program TO find Syntax of Printf() Source Code:- 1:  %{   2:  #include<stdio.h>   3:  #include<ctype.h>   4:  int i=0,j=0;   5:  %}   6:  a "%d"|"%f"|"%c"|"%s"   7:  id [a-zA-Z][a-zA-Z0-9]*   8:  %%   9:  printf\((\"({a}*|.*)*\"(,{id})*\))\; {for(i=0;i<yyleng;i++){if(yytext[i]=='%')   10:  j++;   11:  if(yytext[i]==',')   12:  j--;   13:  }   14:  if(j==0)   15:  printf("\ncorrect");    16:  else    17:  printf("incorrect");   18:  }   19:  %%   20:  main()   21:  { yyin=fopen("file12.c","r");   22:  yylex();   23:  }   24:  int yywrap()   25:  {return 1;   26:  }                    

Lex Code To check the syntax of For loop:- Source code:- 1:  %{   2:  #include<stdio.h> 3:  #include<ctype.h> 4:  int c; 5:  %} 6:  op "++"|"--" 7:  rop "<"|">"|"<="|">="|"=="|"!=" 8:  id [a-zA-Z][a-zA-Z0-9]* 9:  no [0-9]* 10:  pp [\n\t" "] 11:  %% 12:  for\({id}=({no}|{id})\)?(,{id}=({no}|{id}))*\;({id}{rop}({id}|{no}))?\;({id}{op})?(,{id}{op})*\)\;?{pp}*\("{"(.*\n)*.*"}") {printf("correct");c=0;} 13:  .*    {printf("\nwrong");} 14:  %% 15:  main() 16:  { yyin=fopen("file11.c","r"); 17:  yylex(); 18:  } 19:  int yywrap() 20:  {return 1; 21:  }