%{
#include <stdio.h>
#include <ctype.h>
 
int valid = 1; // flag to check validity
%}
 
%%
[0-9]+                  ;   // valid number
[ \t\n]+                ;   // ignore spaces, tabs, newlines
[\+\-\*/\(\)]           ;   // valid operators and parentheses
.                       { valid = 0; }   // invalid character
%%
 
int main() {
    printf("Enter an arithmetic expression: ");
    yylex();
 
    if (valid)
        printf("✅ Valid arithmetic expression\n");
    else
        printf("❌ Invalid arithmetic expression\n");
 
    return 0;
}
 
int yywrap() {
    return 1;
}

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