memoized 1.4.7

Decorators to cache returned values, it helps in reducing the execution time of the function by using LRU Caching.

Overview

• saves the previously computed value

  final sum = Memoized(() => 1.to(999999999).sum());
  print(sum());
  print(sum()); // returned immediately
  

• with LRU Cache (Fibonacci series)

  // Memoized1<ReturnType, ArgumentType>
  late final Memoized1<int, int> fib;
  fib = Memoized1((int n) {
    if (n <= 1) return n;
    return fib(n-1) + fib(n-2);
  });
    
  print(fib(80));
  

  Memoized1~5 maintains an LRU cache that uses a function argument as key and the result value according to the function arguments as value, as follows.

  LruMap<ArgumentType, ReturnType>
  

Installing

dependencies:
  memoized:

import 'package:memoized/memoized.dart';

Memoized

Wrap a function to store the previously computed value and return this value on the next call.

• Basic

  Iterable<int> numbers = 1.to(30000000);
  final calculateSum = (() => numbers.sum()).memo;
    
  print(time(calculateSum));
  print(time(calculateSum));  // It returns the memoized value.
  

• expire

  Iterable<int> numbers = 1.to(30000000);
  final calculateSum = (() => numbers.sum()).memo;
  print(calculateSum());
    
  numbers = 1.to(9043483);
  calculateSum.expire()  // not computed
    
  numbers = 1.to(45000000);
  calculateSum.expire()  // not computed
    
  final value = calculateSum()   // recomputed at this point.
  

• in Class

  class IntervalTimer {
    final List<Duration> timers = [/* durations */];
        
    late final totalDuration = _totalDurationImpl.memo;
    Duration _totalDurationImpl() => timers.fold<Duration>(
      Duration.zero,
    	(p, v) => p + v
    );
  }
  

Memoized1 ~ 5

Decorator to wrap a function with a memoizing callable that saves up to the capacity most recent calls.

• fibonacci

  // Memoized1<ReturnType, ArgumentType>
  late final Memoized1<int, int> fib;
  fib = Memoized1((int n) {
      if (n <= 1) return n;
      return fib(n - 1) + fib(n - 2);
  });
    
  print(fib(90));
    
  

• expire

  print(await fetchDoument('hello')); // returned after 2 seconds.
  fetchDocument.expire('hello');
  print(await fetchDoument('hello')); // also returned after 2 seconds.
  

• in Class

  class Test {
    late final Memoized1<int, int> fib = Memoized1(
      (n) => n <= 1 ? n : fib(n - 1) + fib(n - 2),
    );
  }
  

• capacity

  class Test {
    late final Memoized1<int, int> fib = Memoized1(
      (n) => n <= 1 ? n : fib(n - 1) + fib(n - 2),
      capacity: 10, // default == 128
    );
  }