Loop and filter comparison

loop_and_filter_comparison.dart

import 'dart:math';

// Generate a list of numbers with a configurable length
// The numbers range from 1 to 1 million
// The goal is to then generate a list of all numbers in that list
// which are less than 5 hundred thousand
// This script compares three approaches: 
// typical for loop, iterator-based for loop, and generator-based where method

void main (){
  int valuesLength = 1000000;
  preloadValues(valuesLength);
  
  withForLoop();
  withForEachLoop();
  withWhere();
}

final values = <int>[];

void preloadValues(int sampleSize) {
  values.clear();
  final r = Random();
  for (int i = 0; i < sampleSize; i++) {
    values.add(r.nextInt(1000000));
  }
}

void withForLoop() {
  final start = DateTime.now();
  final results = <int>[];
  
  for (int i = 0; i < values.length; i++) {
    if (values[i] < 500000) {
      results.add(i);
    }
  }
  
  final end = DateTime.now();
  
  print('withForLoop method duration: ${end.difference(start)}');
}

void withForEachLoop() {
  final start = DateTime.now();
  final results = <int>[];
  
  for (int v in values) {
    if (v < 500000) {
      results.add(v);
    }
  }
  
  final end = DateTime.now();
  
  print('withForEachLoop method duration: ${end.difference(start)}');
}

void withWhere() {
  final start = DateTime.now();
  
  final results = values.where((i) => i < 500000).toList();
  
  final end = DateTime.now();
  
  print('withWhere method duration: ${end.difference(start)}');
}