%{
int COMMENT = 0; // Flag to track if inside a comment
%}
 
identifier [a-zA-Z][a-zA-Z0-9]* // Regular expression for identifiers
 
%%
 
#.* {
    // Matches preprocessor directives
    printf("\n%s is a preprocessor directive", yytext);
}
 
int |
float |
char |
double |
while |
for |
struct |
typedef |
do |
if |
break |
continue |
void |
switch |
return |
else |
goto {
    // Matches keywords
    printf("\n\t%s is a keyword", yytext);
}
 
"/*" {
    // Start of a comment
    COMMENT = 1;
    printf("\n\t%s is a COMMENT", yytext);
}
 
"*/" {
    // End of a comment
    COMMENT = 0;
    printf("\n\t%s is a COMMENT END", yytext);
}
 
{identifier}\( {
    // Function definition (identifier followed by '(')
    if (!COMMENT) {
        printf("\nFUNCTION \n\t%s", yytext);
    }
}
 
\{ {
    // Block starts
    if (!COMMENT) {
        printf("\n BLOCK BEGINS");
    }
}
 
\} {
    // Block ends
    if (!COMMENT) {
        printf("BLOCK ENDS ");
    }
}
 
{identifier}(\[[0-9]*\])? {
    // Identifiers, with optional array index
    if (!COMMENT) {
        printf("\n %s IDENTIFIER", yytext);
    }
}
 
\"[^\"]*\" {
    // Strings, allows escape sequences (not yet fully handling all escape sequences)
    if (!COMMENT) {
        printf("\n\t %s is a STRING", yytext);
    }
}
 
[0-9]+ {
    // Numbers
    if (!COMMENT) {
        printf("\n %s is a NUMBER ", yytext);
    }
}
 
\)(\:)? {
    // Matches ')' followed by an optional ':'
    if (!COMMENT) {
        printf("\n\t");
    }
    ECHO; // Print the token
    printf("\n");
}
 
\( {
    // Matches opening '('
    ECHO;
}
 
= {
    // Assignment operator '='
    if (!COMMENT) {
        printf("\n\t %s is an ASSIGNMENT OPERATOR", yytext);
    }
}
 
\<= |
\>= |
\< |
== |
\> |
!= {
    // Relational operators
    if (!COMMENT) {
        printf("\n\t%s is a RELATIONAL OPERATOR", yytext);
    }
}
 
%%
 
int main(int argc, char **argv) {
    FILE *file;
    file = fopen("var.c", "r");
 
    if (!file) {
        printf("could not open the file");
        exit(0);
    }
 
    yyin = file; // Use file input
    yylex();     // Start lexical analysis
    printf("\n");
    return(0);
}
 
int yywrap() {
    return(1); // End of input
}
 

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#include <stdio.h>
int main() {
    int x = 10;
    if (x > 5) {
        printf("x is greater than 5");
    }
}