What is the cleanest way to get the sum of numbers in a collection/list in Dart?

Question

I don't like using an indexed array for no reason other than I think it looks ugly. Is there a clean way to sum with an anonymous function? Is it possible to do it without using any outside variables?

Answer 1

Dart iterables now have a reduce function (https://code.google.com/p/dart/issues/detail?id=1649), so you can do a sum pithily without defining your own fold function:

var sum = [1, 2, 3].reduce((a, b) => a + b); 

Answer 2

int sum = [1, 2, 3].fold(0, (previous, current) => previous + current); 

or with shorter variable names to make it take up less room:

int sum = [1, 2, 3].fold(0, (p, c) => p + c); 

Answer 3

This is a very old question but

In 2022 there is actually a built-in package.

Just import

import 'package:collection/collection.dart';

and call the .sum extension method on the Iterable.

FULL EXAMPLE

import 'package:collection/collection.dart';

void main() {
  final list = [1, 2, 3, 4];
  final sum = list.sum;
  print(sum); // prints 10
}

If the list is empty, .sum returns 0.

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