text: /**
   * See Copyright Notice in picrin.h
   */
  
  #include "picrin.h"
  
  KHASH_DEFINE(s, const char *, pic_sym *, kh_str_hash_func, kh_str_hash_equal)
  
  pic_sym *
  pic_intern_str(pic_state *pic, pic_str *str)
  {
    return pic_intern(pic, pic_str_cstr(pic, str));
  }
  
  pic_sym *
  pic_intern(pic_state *pic, const char *cstr)
  {
    khash_t(s) *h = &pic->syms;
    pic_sym *sym;
    khiter_t it;
    int ret;
    char *copy;
  
    it = kh_put(s, h, cstr, &ret);
    if (ret == 0) {               /* if exists */
      sym = kh_val(h, it);
      pic_gc_protect(pic, pic_obj_value(sym));
      return sym;
    }
  
    copy = pic_malloc(pic, strlen(cstr) + 1);
    strcpy(copy, cstr);
    kh_key(h, it) = copy;
  
    kh_val(h, it) = pic->sQUOTE; /* insert dummy */
  
    sym = (pic_sym *)pic_obj_alloc(pic, sizeof(pic_sym), PIC_TT_SYMBOL);
    sym->cstr = copy;
    kh_val(h, it) = sym;
  
    return sym;
  }
  
  const char *
  pic_symbol_name(pic_state PIC_UNUSED(*pic), pic_sym *sym)
  {
    return sym->cstr;
  }
  
  static pic_value
  pic_symbol_symbol_p(pic_state *pic)
  {
    pic_value v;
  
    pic_get_args(pic, "o", &v);
  
    return pic_bool_value(pic_sym_p(v));
  }
  
  static pic_value
  pic_symbol_symbol_eq_p(pic_state *pic)
  {
    int argc, i;
    pic_value *argv;
  
    pic_get_args(pic, "*", &argc, &argv);
  
    for (i = 0; i < argc; ++i) {
      if (! pic_sym_p(argv[i])) {
        return pic_false_value();
      }
      if (! pic_eq_p(argv[i], argv[0])) {
        return pic_false_value();
      }
    }
    return pic_true_value();
  }
  
  static pic_value
  pic_symbol_symbol_to_string(pic_state *pic)
  {
    pic_sym *sym;
  
    pic_get_args(pic, "m", &sym);
  
    return pic_obj_value(pic_make_str_cstr(pic, sym->cstr));
  }
  
  static pic_value
  pic_symbol_string_to_symbol(pic_state *pic)
  {
    pic_str *str;
  
    pic_get_args(pic, "s", &str);
  
    return pic_obj_value(pic_intern_str(pic, str));
  }
  
  void
  pic_init_symbol(pic_state *pic)
  {
    pic_defun(pic, "symbol?", pic_symbol_symbol_p);
  
    pic_defun(pic, "symbol->string", pic_symbol_symbol_to_string);
    pic_defun(pic, "string->symbol", pic_symbol_string_to_symbol);
  
    pic_defun(pic, "symbol=?", pic_symbol_symbol_eq_p);
  }
  