%{
#include<stdio.h>
int id=0,optr=0,p=0;
%}
%%
[0-9]+ {id++; printf("identifiers are %s\n",yytext);}
[+*/-] {optr++; printf("oprators are %s\n",yytext);}
[(] {p++;}
[)] {p--;}
%%
main()
{
printf("enter an expression \n");
yylex();
if(id==optr+1&&p==0&&optr>=1)
{
printf("this is valid expression \n");
printf("count of operators = %d\n count of identifiers = %d\n ",optr,id);
}
else
printf("this is invalid expression \n");
}
int yywrap()
{
return 1;
}

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