Simple2Code

C Program for Predictive Parser

Written by

admin

in

The following is the C Program for Implementation of functionalities of Predictive Parser.

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

char prol[7][10] = { "S", "A", "A", "B", "B", "C", "C" };
char pror[7][10] = { "A", "Bb", "Cd", "aB", "@", "Cc", "@" };
char prod[7][10] = { "S->A", "A->Bb", "A->Cd", "B->aB", "B->@", "C->Cc", "C->@" };
char first[7][10] = { "abcd", "ab", "cd", "a@", "@", "c@", "@" };
char follow[7][10] = { "$", "$", "$", "a$", "b$", "c$", "d$" };
char table[5][6][10];

int numr(char c)
{
   switch (c)
   {
      case 'S':
         return 0;

      case 'A':
         return 1;

      case 'B':
         return 2;

      case 'C':
         return 3;

      case 'a':
         return 0;

      case 'b':
         return 1;

      case 'c':
         return 2;

      case 'd':
         return 3;

      case '$':
         return 4;
   }

   return (2);
}

int main()
{
   int i, j, k;

   for (i = 0; i < 5; i++)
      for (j = 0; j < 6; j++)
         strcpy(table[i][j], " ");

   printf("The following grammar is used for Parsing Table:\n");

   for (i = 0; i < 7; i++)
      printf("%s\n", prod[i]);

   printf("\nPredictive parsing table:\n");

   fflush(stdin);

   for (i = 0; i < 7; i++)
   {
      k = strlen(first[i]);
      for (j = 0; j < 10; j++)
         if (first[i][j] != '@')
            strcpy(table[numr(prol[i][0]) + 1][numr(first[i][j]) + 1], prod[i]);
   }

   for (i = 0; i < 7; i++)
   {
      if (strlen(pror[i]) == 1)
      {
         if (pror[i][0] == '@')
         {
            k = strlen(follow[i]);
            for (j = 0; j < k; j++)
               strcpy(table[numr(prol[i][0]) + 1][numr(follow[i][j]) + 1], prod[i]);
         }
      }
   }

   strcpy(table[0][0], " ");

   strcpy(table[0][1], "a");

   strcpy(table[0][2], "b");

   strcpy(table[0][3], "c");

   strcpy(table[0][4], "d");

   strcpy(table[0][5], "$");

   strcpy(table[1][0], "S");

   strcpy(table[2][0], "A");

   strcpy(table[3][0], "B");

   strcpy(table[4][0], "C");

   printf("\n--------------------------------------------------------\n");

   for (i = 0; i < 5; i++)
      for (j = 0; j < 6; j++)
      {
         printf("%-10s", table[i][j]);
         if (j == 5)
            printf("\n--------------------------------------------------------\n");
      }
}

Output: Predictive parser in C

The following grammar is used for Parsing Table:
S->A
A->Bb
A->Cd
B->aB
B->@
C->Cc
C->@

Predictive parsing table:

--------------------------------------------------------
          a         b         c         d         $         
--------------------------------------------------------
S         S->A      S->A      S->A      S->A                
--------------------------------------------------------
A         A->Bb     A->Bb     A->Cd     A->Cd               
--------------------------------------------------------
B         B->aB     B->@      B->@                B->@      
--------------------------------------------------------
C                             C->@      C->@      C->@      
--------------------------------------------------------

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