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#include<stdio.h>
#include<string.h>
#include<conio.h>
#include<stdlib.h>
char oper[24][2]={"-","+","=","*","/","&","|","~","<",">","^","%","!","+=","*=","%=","/=","++","--","<=",">=","!=","=="};
char *op="",buf[8],tmpvar[10],tmpopr[10],varlist[10][10]={""},*mstr;
int len,i=0,k,cnt,j, v=0,vl=0,fdup=0,fopr=0,b,ii,c,inval=0;
int lexi(char *);
int valid();
int main()
{
char *str,*temp;
clrscr();
printf("\nEnter the Expression\n");
scanf("%s",mstr);
if(valid()==0)
{
lexi(mstr);
printf("\n\nExpression is Valid\n\n");
}
else
{
printf("\n Invalid Expression ~ brackets");
getch();
return 0;
}
if(inval==0)
{
printf("\n%s\n",op);
printf("\n\nSYMBOL TABLE\n");
for(i=0;i<vl;i++)
printf("\n%s ID%d",varlist[i],i);
getch();
}
return 0;
}
int lexi(char *str)
{
len=strlen(str);
while(i<len)
{
if(str[i]=='('||str[i]==')')
{
sprintf(buf,"%c",str[i]);
strcat(op,buf);
i++;
}
v=0;
while(isalpha(str[i])||isdigit(str[i]))
{
tmpvar[v]=str[i];
v++;
i++;
}
tmpvar[v]='\0';
fdup=0;
if(!isdigit(tmpvar[0]))
{
for(cnt=0;cnt<=vl;cnt++)
if(strcmp(tmpvar,varlist[cnt])==0)
{
sprintf(buf,"ID%d",cnt);
strcat(op,buf);
fdup=1;
}
if(fdup!=1)
{
strcpy(varlist[vl],tmpvar);
sprintf(buf,"ID%d",vl);
strcat(op,buf);
vl++;
}
}
else
strcat(op,tmpvar);
if(i==0||!isalpha(str[0])||(!isalpha(str[len-1])&&
!isdigit(str[len-1]))&&str[len-1]!=')')
{
printf("\nInvalid expression \n");
inval++;
getch();
return 0;
}
k=0;
if(str[i]=='('||str[i]==')')
{
sprintf(buf,"%c",str[i]);
strcat(op,buf);
i++;
}
while(!isalpha(str[i])&&!isdigit(str[i])&&str[i]!='('&&str[i]!=')')
{
tmpopr[k]=str[i];
k++;
i++;
}
tmpopr[k]='\0';
fopr=0;
for (j=0;j<24;j++)
if(strcmp(tmpopr,oper[j])==0)
{
strcat(op,tmpopr);
fopr=1;
break;
}
if(str[len-1]!=')'&&(strcmp(tmpopr,"")!=0&&fopr==0))
{
printf("\nInvalid Expression \n");
inval++;
getch();
return 0;
}
}
}
int valid()
{
b=ii=0;
while(mstr[ii++]!='\0')
{
if(mstr[ii]=='(')
{
b++;
ii++;
if (isalpha(mstr[ii]))
continue;
else
{
printf("\n Invalid expression ~ brackets");
inval++;
getch();
exit(0);
}
}
if(mstr[ii]==')')
{
b--;
ii++;
}
}
return b;
}