SCM_INTERNAL void scm_i_string_stop_writing (void);
SCM_INTERNAL int scm_i_is_narrow_string (SCM str);
SCM_INTERNAL scm_t_wchar scm_i_string_ref (SCM str, size_t x);
+SCM_INTERNAL int scm_i_string_contains_char (SCM str, char c);
SCM_INTERNAL int scm_i_string_strcmp (SCM sstr, size_t start_x, const char *cstr);
SCM_INTERNAL void scm_i_string_set_x (SCM str, size_t p, scm_t_wchar chr);
/* internal functions related to symbols. */