Beginner: L1 Parsing Table Syntax Error [closed] - c++

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I'm a CS Student working on a code to implement but having hard time running it.
Can you please help me out in running this L1 Parsing Table.
May be i'm doing some stupid syntax mistake.
I'll be very thankful to your replies.
Cheers!
#include <iostream.h>
#include <conio.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
void main()
{
clrscr();
int i=0,j=0,k=0,m=0,n=0,o=0,o1=0,var=0,l=0,f=0,c=0,f1=0;
char str[30],str1[40]="E",temp[20],temp1[20],temp2[20],tt[20],t3[20];
strcpy(temp1,'\0');
strcpy(temp2,'\0');
char t[10];
char array[6][5][10] = {
"NT", "<id>","+","*",";",
"E", "Te","Error","Error","Error",
"e", "Error","+Te","Error","\0",
"T", "Vt","Error","Error","Error",
"t", "Error","\0","*Vt","\0",
"V", "<id>","Error","Error","Error"
};
cout << "\n\tLL(1) PARSER TABLE \n";
for(i=0;i<6;i++)
{
for(j=0;j<5;j++)
{
cout.setf(ios::right);
cout.width(10);
cout<<array[i][j];
}
cout<<endl;
}
cout << endl;
cout << "\n\tENTER THE STRING :";
gets(str);
if(str[strlen(str)-1] != ';')
{
cout << "END OF STRING MARKER SHOULD BE ';'";
getch();
exit(1);
}
cout << "\n\tCHECKING VALIDATION OF THE STRING ";
cout <<"\n\t" << str1;
i=0;
while(i<strlen(str))
{
again:
if(str[i] == ' ' && i<strlen(str))
{
cout << "\n\tSPACES IS NOT ALLOWED IN SOURSE STRING ";
getch();
exit(1);
}
temp[k]=str[i];
temp[k+1]='\0';
f1=0;
again1:
if(i>=strlen(str))
{
getch();
exit(1);
}
for(int l=1;l<=4;l++)
{
if(strcmp(temp,array[0][l])==0)
{
f1=1;
m=0,o=0,var=0,o1=0;
strcpy(temp1,'\0');
strcpy(temp2,'\0');
int len=strlen(str1);
while(m<strlen(str1) && m<strlen(str))
{
if(str1[m]==str[m])
{
var=m+1;
temp2[o1]=str1[m];
m++;
o1++;
}
else
{
if((m+1)<strlen(str1))
{
m++;
temp1[o]=str1[m];
o++;
}
else
m++;
}
}
temp2[o1] = '\0';
temp1[o] = '\0';
t[0] = str1[var];
t[1] = '\0';
for(n=1;n<=5;n++)
{
if(strcmp(array[n][0],t)==0)
break;
}
strcpy(str1,temp2);
strcat(str1,array[n][l]);
strcat(str1,temp1);
cout << "\n\t" <<str1;
getch();
if(strcmp(array[n][l],'\0')==0)
{
if(i==(strlen(str)-1))
{
int len=strlen(str1);
str1[len-1]='\0';
cout << "\n\t"<<str1;
cout << "\n\n\tENTERED STRING IS VALID";
getch();
exit(1);
}
strcpy(temp1,'\0');
strcpy(temp2,'\0');
strcpy(t,'\0');
goto again1;
}
if(strcmp(array[n][l],"Error")==0)
{
cout << "\n\tERROR IN YOUR SOURCE STRING";
getch();
exit(1);
}
strcpy(tt,'\0');
strcpy(tt,array[n][l]);
strcpy(t3,'\0');
f=0;
for(c=0;c<strlen(tt);c++)
{
t3[c]=tt[c];
t3[c+1]='\0';
if(strcmp(t3,temp)==0)
{
f=0;
break;
}
else
f=1;
}
if(f==0)
{
strcpy(temp,'\0');
strcpy(temp1,'\0');
strcpy(temp2,'\0');
strcpy(t,'\0');
i++;
k=0;
goto again;
}
else
{
strcpy(temp1,'\0');
strcpy(temp2,'\0');
strcpy(t,'\0');
goto again1;
}
}
}
i++;
k++;
}
if(f1==0)
cout << "\nENTERED STRING IS INVALID";
else
cout << "\n\n\tENTERED STRING IS VALID";
getch();
}
OUTPUT
LL(1) PARSER TABLE
NT <id> + * ;
E Te Error Error Error
e Error +Te Error
T Vt Error Error Error
t Error *Vt
V <id> Error Error Error
ENTER THE STRING :<id>+<id>*<id>;
CHECKING VALIDATION OF THE STRING
E
Te
Vte
<id>te
<id>e
<id>+Te
<id>+Vte
<id>+<id>te
<id>+<id>*Vte
<id>+<id>*<id>te
<id>+<id>*<id>e
<id>+<id>*<id>
ENTERED STRING IS VALID
[/Code]

Answer 1

So, you want a code inspection / code review. Here it goes:
C++ vs. C
Your program looks like it is C, but your question tag says C++. So, I'll view it from the C++ perspective.
Switch your header files to C++:
#include <iostream>
#include <string>
#include <cstdlib>
Note there is no ".h" suffix in the header names.
Console I/O
The conio.h header file is compiler specific. You didn't mention which compiler you are using, so many of us can't load your source and help you.
The clrscr() function is not necessary and often times, clearing the screen erases information that you may need later. BTW, it is not portable because not all platforms have screens.
void main
The main function returns int, always.
Variable Names
The C++ language specification allows for at least 32 characters in an identifier. More characters are allowed but only the first 32 are used to determine duplicates.
So use them. Single letters only reduce your typing time. Descriptive names allow other people, and you, to easily understand how your code is working. Do you know what all of those variable are used for, without reading any other documentation?
Style -- one declaration per line
Declare one variable per line. Easier to maintain, easier to read.
Spaces?
Spaces cost very little build time and don't effect execution speed. They add clarity, use them.
The general rules are one space between variables and operators; one space after a comma.
Character Arrays
Don't use them, the cause problems. Since your question is tagged C++, use std::string instead.
strcpy for one character
Don't use strcpy for one character, just assign it directly:
temp1[0] = '\0';
By the way, strcpy is dangerous, use strncpy instead; notice the letter 'n'.
Const
Use it. Things that don't change should be declared as const to prevent mistakes and allowing the compiler to find this mistakes. Also, character constants (a.k.a. literals) are constant and can't be changed.
Mapping Tables
Three dimensions? Really?
How about something easier to understand, such as a table of structures:
struct Token_Entry
{
const char * token_text;
unsigned int token_ID;
};
const Token_Entry token_table[] =
{
{TOKEN_NT, "NT"},
{TOKEN_ID, "<id>"},
{TOKEN_PLUS, "+"},
// ...
};
const unsigned int Number_Of_Token_Entries =
sizeof(token_table) / sizeof(token_table[0]);
Avoid gets, it's dangerous.
The gets reads input regardless of quantity. If you allocate 5 slots and the User types 10 letters, you will overrun your buffer. Very bad.
Use fgets if you must or switch to C++ and use getline(std::string).
Avoid the exit function
The proper technique is to use return in the main function. This allows proper clean up of variables. The exit function is a little bit more dangerous.
No Gotos and labels
Read up on loops in your favorite, correct, C++ text. Expecially the break and continue keywords.
One assignment per line
Carriage returns, linefeeds and newlines are free, use them. One assignment per line. It slows down the compilation process by either microseconds or nanoseconds; in otherwords, the time required to process line ending characters is negligible.
Use parenthesis
Grouping logical statements with parenthesis may not be necessary if you have memorized the precedence table, but they make the code more readable:
while ((m < strlen(str1)) && (m < strlen(str)))
Compute constants once
For example, the length of the string will not change during your analyzing loops. So store it into a constant variable:
const unsigned int length_str1 = str1.length(); // Since you will be using std::string.
const unsigned int length_str = strlen(str); // Or if you insist on C-style strings.
while ((m < length_str1) && (m < length_str))
Unsigned vs. signed integers
One of my pet peeves. Use int (a.k.a. signed int) if the value can be negative; otherwise use unsigned int. For example, a text length can't be negative. What does a string of length -5 look like?
Comment your code
Tell the reader what you are doing and why. Don't talk about assigning variables. For example, why is k incremented at the end of the loop? Why are you setting temp to null in one section but not the other. What is the f1 variable used for? Set verbosity = maximum.
Use a debugger
Since you didn't comment the code, used single letter variable names, your code will take a lot of time to understand. You can help out by using a debugger. A debugger allows you to execute lines one at a time (a.k.a. single stepping), and print out or display the values in your variables. A lot faster than the ancient art of adding print statements for your variables at different locations in your code.
Also, using a debugger is a faster method to test and evaluate your program than posting it on the web, especially here.