%{
#include <stdio.h>
#include <ctype.h>
 
int isValid = 1; 
%}
 
%%
[ \t\n]+               ;
[a-zA-Z][a-zA-Z0-9]*   { printf("Identifier: %s\n", yytext); }
"+"|"-"|"*"|"/"        { printf("Operator: %s\n", yytext); }
[0-9]+                
"="                    { printf("Assignment: %s\n", yytext); }
.                      { isValid = 0; }
%%
 
int main(void) {
    printf("Enter an arithmetic expression:\n");
    yylex();
 
    if (isValid) {
        printf("The expression is valid.\n");
    } else {
        printf("The expression is invalid.\n");
    }
 
    return 0;
}
 
int yywrap() {
    return 1;
}

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