RangeExtensions

This package enables the usage of System.Range in foreach expressions and provides extensions to integrate it with LINQ as a faster replacement to Enumerable.Range.

• Correctness is verified against IEnumerable<int> and Enumerable.Range behavior;
• Implementation tries its best to make abstractions either zero-cost or reasonably close to that. For critical paths, performance is tuned to be allocation-free and on par with regular for loops

Features

Range enumeration

foreach (var i in ..100) // you can write 0..Length as just ..Length
{
    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);
}

Select and Where

var floats = (0..100).Select(i => (float)i);
var odd = (0..100).Where(i => i % 2 != 0);

var randomNumbers = (0..1000)
    .Select(_ => Random.Shared.Next())
    .ToArray();

Collecting to array or list

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

Aggregate

var digits = (0..10)
    .Aggregate(new StringBuilder(), (sb, i) => sb.Append(i))
    .ToString();

Assert.Equal("0123456789", digits);

Other LINQ specializations

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

Tl;Dr: In .NET 7, foreach (var i in 0..Length) has the same performance as for loop. In other scenarios, RangeExtensions is 2-10x faster than Enumerable.Range (DynamicPGO helps the latter quite a bit)

BenchmarkDotNet=v0.13.2, OS=macOS 13.1 (22C65) [Darwin 22.2.0]
Apple M1 Pro, 1 CPU, 8 logical and 8 physical cores
.NET SDK=8.0.100-alpha.1.22620.11
  [Host]     : .NET 7.0.1 (7.0.122.56804), Arm64 RyuJIT AdvSIMD
  DefaultJob : .NET 7.0.1 (7.0.122.56804), Arm64 RyuJIT AdvSIMD

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

DOTNET_TieredPGO=1
DOTNET_ReadyToRun=0