Question

Write a lex program that can identify each of the following tokens. The program should produce a line
for each token where the first word is token itself followed by the token type.

• Identifiers: name of variables and functions (identifier name should be started by a letter
followed by letters or digits and maximum eight characters in length).

• Keywords: if, then, else, for, while, do, switch, case etc.
• Numbers: integer, float (float number format that supports in C++/Java)

• Operators:
• Arithmetic operators (+,-,*,/)
• Relational operators (<, <=, >, >=, ==, !=)
• Conditional operators ( &&, ||, !, )
• Increment/decrement operators (++, --)
• Bitwise operators (&, |)
• Assignment operator (=)

• Special Symbols: (, ), {,},; .. etc

Answer 1

SOLUTION:-

%option noyywrap

%{

            #include<stdio.h>

%}

TYPE int|char|bool|float|double|void|for|do|while|if|else|return|switch|case|then

DIGIT [0-9]

%%

{TYPE} {printf("Token %s is keywords\n ",yytext);}

[a-zA-Z_][a-zA-Z0-9]* {printf("Token %s is an identifiers\n ",yytext);}

"+"|"-"|"*"|"/" {printf("Token %s is arithmatic operators\n",yytext);}

"=="|"!="|">"|"<"|"<="|">=" {printf("Token %s is relational operators\n",yytext);}

"&&"|"||"|"!" {printf("Token %s is conditional operators\n",yytext);}

"++"|"--"   {printf("Token %s is Increment/decrement operators\n",yytext);}

"&"|"|" {printf("Token %s is bitwise operators\n",yytext);}

"=" {printf("Token %s is assignment operators\n",yytext);}

^{DIGIT}+                               {printf("Token %s is integer constant.\n",yytext);}

^{DIGIT}+[.]+{DIGIT}+            {printf("Token %s is floating number constant.\n",yytext);}

"("|")"|"{"|"}"|";" {printf("Token %s is special symbols \n",yytext);}

.                         ;

%%

int main()                                              

{

printf("Enter herer :\n");

yylex();

return 0;

}