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Creation of Symbol Table in Lex to check the Expression


digit [0-9]
letter [a-zA-Z]
keyword int|float|double
operator [-]|[*]|[+]|[/]
space [' ']
comma [,]
semicolon [;]
equal [=]

%{
#include<string.h>
void symb_tab(char data[]);
void check_data(char s[]);
void display();
void valid();
void check_more();       


char identifier[10][10],datatype[10][10],key[10],iden[10],temp[10];
int i=0,j=0,key_insert=0,cnt=0,k=0,t=0,r=0,exists=0,m=0,e_cntr=0;
%}


%%

{keyword}{space}{letter}({letter}|{digit})*({comma}{space}*{letter}({letter}|{digit})*)*{semicolon} {symb_tab(yytext);}
{letter}+{digit}*{equal}{digit}*{letter}({letter}|{digit})*({operator}{digit}*{letter}({letter}|{digit})*)*{semicolon} {check_data(yytext);}
{semicolon} {valid();}
. {printf("nothing");;}

%%

void symb_tab(char data[])
{

    // To reach the end of the sentence
    while(data[i]!=';')
    {
        if(data[i]!=' ' && key_insert==0)
        {
            key[j]=data[i];
            j++;
           
        }
        else
        {
            key_insert=1;
            if(data[i]!=',' && data[i]!=' ')
            {
                iden[k]=data[i];   
                k++;
            }
            else
            {
               
                strcpy(identifier[cnt],iden);
                strcpy(datatype[cnt],key);   
                cnt++;
                k=0;

                // To clear an array               
                for(r=0;r<10;r++)
                {
                    iden[r]='\0';
                }   
               
            }
               
        }
        i++;
       
    }

    strcpy(identifier[cnt],iden);
    strcpy(datatype[cnt],key);   
    cnt++;
   


}

void check_data(char s[])
{



    i=0,j=0,m=0;
    while(s[i]!=';')
    {
        if(s[i]!='+' && s[i]!='-' && s[i]!='*' && s[i]!='/' && s[i]!='=')
        {
            temp[m]=s[i];
            m++;
           
        }
        else
        {

            check_more();
            m=0;

        }

        i++;
    }

    check_more();       


}

void check_more()
{
            e_cntr++;

            for(j=0;j<10;j++)
            {
                if((strcmp(identifier[j],temp))==0)
                {
                    exists++;
               
                   
                }
            }
           
           
            for(k=0;k<10;k++)
            {
                temp[k]='\0';
            }

}

void valid()
{

        if(e_cntr==exists)
        {
            printf("\n Valid expression");
        }
        else
        {
            e_cntr=0;
            exists=0;
            printf("\n Invalid expression");
        }
}

/*
void display()
{
    for(t=0;t<cnt;t++)
    {
        printf("\n%s\t%s",datatype[t],identifier[t]);
    }
}
*/

int main(void)
{
    yylex();
   
    return(0);
}





Output:




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