memoized 1.1.2

Useful function wrappers for avoiding unnecessary computation. it makes the function return a memoized(cached) value.

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.
  

• Update

  Iterable<int> numbers = 1.to(30000000);
  final calculateSum = (() => numbers.sum()).memo;
    
  numbers = 1.to(9043483);
  calculateSum.update();  // recomputed
  

• Lazy Update

  Iterable<int> numbers = 1.to(30000000);
  final calculateSum = (() => numbers.sum()).memo;
  print(calculateSum());
    
  numbers = 1.to(9043483);
  calculateSum.requestUpdate();  // not computed
    
  numbers = 1.to(45000000);
  calculateSum.requestUpdate();  // 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

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

• fibonacci

  // Memoized1<RetrunType, ArgumentType>
  final fibMemo = Memoized1<BigInt, BigInt>((n, self) {
    if (n <= BigInt.one) return n;
    return self(n - BigInt.one) + self(n - BigInt.two);
  });
    
  // returns 222232244629420445529739893461909967206666939096499764990979600 
  // very quickly
  print(fibMemo(BigInt.parse('300')));
    
  

• count vowels

  final countVowelMemo = Memoized1<int, String>((str, _) {
    int count = 0;
    for (int i = 0; i < str.length; i++) {
      if ("aeiouAEIOU".contains(str[i])) count++;
    }
    return count;
  });
  

• Cache capacity

  final fibMemo = Memoized1<BigInt, BigInt>(
    (n, self) {
      if (n <= BigInt.one) return n;
      return self(n - BigInt.one) + self(n - BigInt.two);
    },
    capacity: 1, // modified, default == 128
  );
    
  // Oh, god
  print(fibMemo(BigInt.parse('300')));