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

/* global variables */

int tok;

extern FILE *yyin;

void start (void) {
  yyin = fopen("recdesc_in.txt", "r");
  tok = yylex();
  printf("Recognized %d\n", tok);
}

void advance(void) {
  tok = yylex();
  printf("Recognized %d\n", tok);
}

void stop (void) {
  fclose(yyin);
}

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

void eat(enum token t) {
  printf("Reading token %4d, expecting %4d\n", tok, 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();
  stop();

  return 0;
}