darq 1.2.1

The power of lazy-evaluated enumerables in your hands! (A port of functional LINQ from the .NET library.)

example/main.dart

import 'package:darq/darq.dart';

void main() {
  benchmark();
  // sandbox();
}

void sandbox() {
  final list = ['a', 'b', 'b', 'c'];
  print(list.distinct((s) => s.hashCode).toList());
}

typedef Foo2<T1, T2> = T2 Function(T1 a);
typedef Foo3<T1, T2, T3> = T3 Function(T1 a, T2 b);

class Bar<A> {
  final List<A> outer;
  Bar(this.outer);

  void run<B, C, D>(
    List<B> inner,
    Foo2<A, C> outerSelector,
    Foo2<B, C> innerSelector,
    Foo3<A, B, D> resultSelector,
  ) {
    print([A, B, C, D]);
    print([
      outer.runtimeType,
      inner.runtimeType,
      outerSelector.runtimeType,
      innerSelector.runtimeType,
      resultSelector.runtimeType
    ]);
  }
}

class Person {
  final String name;
  Person(this.name);
}

class Pet {
  final String name;
  final String owner;
  Pet(this.name, this.owner);
}

void benchmark() {
  final source = List.generate(1000000, (i) => i);
  final iterations = 100;
  final benchmarks = List<double>.generate(iterations, (_) => -1);

  // LINQ style
  for (var i = 0; i < iterations; i++) {
    final start = DateTime.now();

    // ======================BENCHMARK START=============================
    final result = source.groupBy((i) => i % 3).select((g, i) => g.average());
    result.consume();
    // ======================BENCHMARK END===============================

    final end = DateTime.now();

    benchmarks[i] =
        (end.microsecondsSinceEpoch - start.microsecondsSinceEpoch) / 1000000;
  }

  print('Average execution time in seconds (LINQ): ${benchmarks.average()}');

  // Vanilla Style
  for (var i = 0; i < iterations; i++) {
    final start = DateTime.now();

    // ======================BENCHMARK START=============================
    final result = <List<int>>[[], [], []];
    for (var i in source) {
      result[i % 3].add(i);
    }
    for (var g in result) {
      var total = 0;
      for (var i in g) {
        total += i;
      }
      final _ = total / g.length;
      // Go something with the value
    }
    // ======================BENCHMARK END===============================

    final end = DateTime.now();

    benchmarks[i] =
        (end.microsecondsSinceEpoch - start.microsecondsSinceEpoch) / 1000000;
  }

  print('Average execution time in seconds (Vanilla): ${benchmarks.average()}');
}