RangeExtensions

Extensions for Range type to support foreach and RangeEnumerable that implements IEnumerable<int>.

• Correctness is verified against standard IEnumerable<int> and Enumerable.Range behavior
• Performance is hand tuned to produce efficient native code with no allocations as long as RangeEnumerable isn't boxed into IEnumerable<int> (same applies to enumerator)

Features

Range enumeration

foreach (var i in 0..100)
{
    Console.WriteLine(i);
}

Reverse range enumeration

for (var i = 100 - 1; i >= 0; i--)
{
    Console.WriteLine(i);
}

// Can be written as
foreach (var i in 100..0)
{
    Console.WriteLine(i);
}

Collecting to array or list

var numbers = (0..100).ToArray();

IEnumerable<int> (some methods have bespoke implementations for performance)

var enumerable = (..100).AsEnumerable();

var sum = enumerable.Sum();
var count = enumerable.Count();
var average = enumerable.Average();
var firstTen = enumerable.Take(10);
var reversed = enumerable.Reverse();
// and others.

Performance

In short: 10x fast vs Enumerable.Range() and as fast as a plain for loop (there's small fixed overhead to check range correctness).

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.22000
AMD Ryzen 7 5800X, 1 CPU, 16 logical and 8 physical cores
.NET SDK=7.0.100-rc.1.22363.32
  [Host]   : .NET 7.0.0 (7.0.22.36203), X64 RyuJIT
  ShortRun : .NET 7.0.0 (7.0.22.36203), X64 RyuJIT

Job=ShortRun  IterationCount=3  LaunchCount=1  
WarmupCount=3