#include <stdio.h>
#include "recdesc.h"


/* global variables */
TOKTYPE tstr [] = {IF, NUM, EQ, NUM, THEN, PRINT,  ELSE, PRINT, NUM}; 
int tstr_ptr;
TOKTYPE tok;

void start (void) {
  tstr_ptr = 0;
  tok = tstr[0];
}

void advance(void) {
  tstr_ptr = tstr_ptr + 1;
  tok = tstr[tstr_ptr];
}

void error(void) {
  printf("Error in token %4d\n", tok);
}

void eat(TOKTYPE t) {
  if (tok == t) advance(); else error();
}

/* Implementation of the grammar */

void E (void) { 
  eat(NUM); eat(EQ); eat(NUM); 
  printf("Recognized rule E\n"); 
}

void S (void) { 
  switch (tok) {
  case PRINT: 
    eat(PRINT); eat(NUM);
    printf("Recognized rule S 1\n"); 
    break;
  case IF: 
    eat(IF); E(); eat(THEN); S(); eat(ELSE); S();
    printf("Recognized rule S 2\n"); 
    break;
  default: error();
  }
}

/* Main function */

int main (void) {
  start();
  S();
  return 0;
}