prog3.y

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

char STACK[20]="\0";
int TOP=-1,flag=0;
int B_ptr = 0;
char BUFFER[20],G_prod[20];

char table [3][3][10] = {
  "NT", "a","b",
  "A", "aBa","Error",
  "B", "Îμ","bB",
};

char pop()
{
  char ch;
  ch = STACK[TOP--];
  return ch;
}

void push(char ch)
{
  STACK[++TOP] = ch;
}

void stack_content()
{
  if (TOP != -1)
  {
    int i = 0;
    printf("\nstack content: ");
    while(i <= TOP)
    {
      printf("%c",STACK[i++]);
    }
    printf("\n");
  }
  return;
}

int isterm(char c)
{
  if (c >= 'a' && c <= 'z')
    return 1;
  else
    return 0;
}

int Parser_table(char stack_top,char buf_value,int flag)
{
  int r,c;

  switch(stack_top)
  {
    case 'A' : r = 1; break;
    case 'B' : if(flag<=5) r = 2; else r = 3;
  }

  switch(buf_value)
  {
    case 'a' : c = 1; break;
    case 'b' : c = 2;
  }

  if (strcmp(table[r][c],"error") == 0)
    return 0;

  if (strcmp(table[r][c],"Îμ") != 0)
  {
    strcpy(G_prod,table[r][c]);
  }

  return 1;
}

int main()
{
  int i,j,stln;
  printf("LL(1) PARSER TABLE \n");

  for(i=0;i<3;i++)
  {
    for(j=0;j<3;j++)
    {
      printf("%s\t",table[i][j]);
    }
    printf("\n");
  }

  printf("\n");
  printf("ENTER THE STRING into the Buffer and also give a ';' as the terminator: ");
  scanf("%s",BUFFER);
  printf("\n THE STRING in the Buffer is %s",BUFFER);

  if(BUFFER[strlen(BUFFER)-1] != ';')
  {
    printf("END OF STRING MARKER SHOULD BE ';'");
    exit(0);
  }

  push('$');
  push('A');

  while(STACK[TOP] != '$') // Stack is not Empty
  {
    flag++;

    if (STACK[TOP] == BUFFER[B_ptr]) // X is a
    {
      printf("\n1.The poped item is - %c,",pop());
      B_ptr++;
      printf("\t buffer cont - %.*s",strlen(BUFFER),BUFFER+B_ptr);
    }

    else if(isterm(STACK[TOP])) // is X is terminal
    {
      printf("\n2. $ %c",STACK[TOP]);
      printf("\t Error in Parsing \n");
    }

    else
      if (!Parser_table(STACK[TOP],BUFFER[B_ptr],flag))
        printf("3. Error Entry in Parse Table ");
      else
        if (Parser_table(STACK[TOP],BUFFER[B_ptr],flag))
        {
          if (flag < 6 && strcmp(G_prod,"Îμ") != 0)
          {
            printf("\n4.1 flag = %d, prod id- %s*\t",flag,G_prod);
            pop();
            stln = strlen(G_prod);
            for(i=stln-1;i>=0;i--)
              push(G_prod[i]);
            stack_content();
          }
          else
          {
            stack_content();
            printf("\n4.2 flag = %d *reduce by %s*",flag,"B->Îμ");
            pop();
            printf("\t buffer content is %c",BUFFER[B_ptr]);
          }
        }
    }

  if (STACK[TOP] == '$' && BUFFER[B_ptr] == ';')
    printf("\n** The string is accepted **");

  else
    printf("\n** The string is not accepted **");
}