You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: num.rs
    path of file: ./repos/rant/src/format
    
    the code of the file until where you have to start completion: use std::cmp::Ordering;

use crate::{TryFromRant, InternalString, TryIntoRant, RantValue, ValueError};

const DEFAULT_SIGN_POSITIVE: &str = "+";
const DEFAULT_SIGN_NEGATIVE: &str = "-";
const DEFAULT_NAN: &str = "NaN";
const DEFAULT_INFINIT
    
  fn get_decimal_digit(&self, digit_index: usize) -> Option<char> {
    if digit_index > 9 { return None }
    Some(match self {
      Self::WestArabic => DIGITS_DEFAULT[digit_index],
      Self::EastArabic => DIGITS_ARABIC_E[digit_index],
      Self::Persian => DIGITS_PERSIAN[digit_index],
      _ => return None
    })
  }