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

unsigned char cells[1024];
unsigned char *ptr = cells;

void error(char c) {
   fprintf(stderr, "ERROR: Unexpected token, %c\n", c);
   exit(1);
}

char *parse(char *src) {

   char *start = src;

   while (*src != '\0') {
      switch (*src) {
         case 0: return NULL;
         case '.': printf("%c", (*ptr)); break;
         case ',': *ptr = getc(stdin); break;
         case '+': (*ptr)++; break;
         case '-': (*ptr)--; break;
         case '>': ptr++; break;
         case '<': ptr--; break;
         case '[': src = parse(++src); break;
         case ']': 
            if (*ptr == 0) return src;
            src = start;
            continue;
      }

      src++;
   }

   return NULL;
}

int main(int argc, char *argv[]) {

   if (argc != 2) return 1;

   FILE *file = fopen(argv[1], "r");
   if (!file) return 1;

   fseek(file, 0, SEEK_END);
   size_t size = ftell(file);
   rewind(file);

   char *src = malloc(size);
   fread(src, 1, size, file);

   if (parse(src) != NULL) {
      error('[');
   }

   return 0;
}