Lexicographical Order #

A string generator that helps to implement a lexicographical order(lexical order).

This makes reordering transactions faster and simpler.

Installing #

dependencies:
  lexicographical_order: 

import 'package:lexicographical_order/lexicographical_order.dart';

Usage #

• Get a string between two strings in a lexicographical order.

  final mid = between(prev: 'B', next: 'D');
  final list = [mid, 'D', 'B'];
  assert(listEqauls(list..sort(), ['B', mid, 'D']);
  

• Generates order keys.

  final keyCount = 100;
  final orderKeys = generateOrderKeys(keyCount);
  

  this is useful for generating first order keys.

Caution #

The between function accepts only allowed characters as arguments

more precisely, the following code must return true.

final prev = prevEntity.orderKey;
final next = nextEntity.orderKey;
return LexOrderValidator().checkBetweenArgs(prev: prev, next: next);

The LexOrderValidator checks the follwing constraints:

1. both prev and next must be empty or composed of alphabets.

2. next must not be 'A'

3. prev and next must not be equal to each other.

4. if both prev and next are not empty, prev must not precede next in the lexicographical order. for example:

   between(prev: 'C', next: 'B');
   

   that argument combination is invalid because between cannot calculate the string between 'C' and 'B'.

In debug mode, you get an exception if you violate the above constraints. but not in release mode. you can check the constraints manually by using LexOrderValidator.