Is there a C# type for representing an integer Range?

Question

I have a need to store an integer range. Is there an existing type for that in C# 4.0?

Of course, I could write my own class with int From and int To properties and build in proper logic to ensure that From <= To. But if a type already exists, I'd of course rather use that.

Answer 1

I found it best to roll my own. Some people use Tuples or Points, but in the end you want your Range to be extensive and provide some handy methods that relate to a Range. It's also best if generic (what if you need a range of Doubles, or a range of some custom class?) For example:

/// <summary>The Range class.</summary>
/// <typeparam name="T">Generic parameter.</typeparam>
public class Range<T> where T : IComparable<T>
{
    /// <summary>Minimum value of the range.</summary>
    public T Minimum { get; set; }

    /// <summary>Maximum value of the range.</summary>
    public T Maximum { get; set; }

    /// <summary>Presents the Range in readable format.</summary>
    /// <returns>String representation of the Range</returns>
    public override string ToString()
    {
        return string.Format("[{0} - {1}]", this.Minimum, this.Maximum);
    }

    /// <summary>Determines if the range is valid.</summary>
    /// <returns>True if range is valid, else false</returns>
    public bool IsValid()
    {
        return this.Minimum.CompareTo(this.Maximum) <= 0;
    }

    /// <summary>Determines if the provided value is inside the range.</summary>
    /// <param name="value">The value to test</param>
    /// <returns>True if the value is inside Range, else false</returns>
    public bool ContainsValue(T value)
    {
        return (this.Minimum.CompareTo(value) <= 0) && (value.CompareTo(this.Maximum) <= 0);
    }

    /// <summary>Determines if this Range is inside the bounds of another range.</summary>
    /// <param name="Range">The parent range to test on</param>
    /// <returns>True if range is inclusive, else false</returns>
    public bool IsInsideRange(Range<T> range)
    {
        return this.IsValid() && range.IsValid() && range.ContainsValue(this.Minimum) && range.ContainsValue(this.Maximum);
    }

    /// <summary>Determines if another range is inside the bounds of this range.</summary>
    /// <param name="Range">The child range to test</param>
    /// <returns>True if range is inside, else false</returns>
    public bool ContainsRange(Range<T> range)
    {
        return this.IsValid() && range.IsValid() && this.ContainsValue(range.Minimum) && this.ContainsValue(range.Maximum);
    }
}

Answer 2

Ranges and Indices are released with C#8.0 and .NET Core.

You are now able to do

string[] names =
{
    "Archimedes", "Pythagoras", "Euclid", "Socrates", "Plato"
};
foreach (var name in names[1..4])
{
    yield return name;
}

Check out https://blogs.msdn.microsoft.com/dotnet/2018/12/05/take-c-8-0-for-a-spin/ for more detail.

Answer 3

Just a small class I wrote which could be helpful for someone:

    public class Range
    {
        public static List<int> range(int a, int b)
        {
            List<int> result = new List<int>();

            for(int i = a; i <= b; i++)
            {
                result.Add(i);
            }

            return result;
        }

        public static int[] Understand(string input)
        {
            return understand(input).ToArray();
        }

        public static List<int> understand(string input)
        {
            List<int> result = new List<int>();
            string[] lines = input.Split(new char[] {';', ','});

            foreach (string line in lines)
            {
                try
                {
                    int temp = Int32.Parse(line);
                    result.Add(temp);
                }
                catch
                {
                    string[] temp = line.Split(new char[] { '-' });
                    int a = Int32.Parse(temp[0]);
                    int b = Int32.Parse(temp[1]);
                    result.AddRange(range(a, b).AsEnumerable());
                }
            }

            return result;
        }
    }

Then you just call:

Range.understand("1,5-9,14;16,17;20-24")

And the result looks like:

List<int>
    [0]: 1
    [1]: 5
    [2]: 6
    [3]: 7
    [4]: 8
    [5]: 9
    [6]: 14
    [7]: 16
    [8]: 17
    [9]: 20
    [10]: 21
    [11]: 22
    [12]: 23
    [13]: 24

Answer 4

Improving upon @andrius-naruševičius very helpful answer to make it more idiomatic and readily customisable

/// <summary>
/// http://stackoverflow.com/questions/5343006/is-there-a-c-sharp-type-for-representing-an-integer-range
/// </summary>
public class Range
{
    readonly static char[] Separators = {','};

    public static List<int> Explode(int from, int to)
    {
        return Enumerable.Range(from, (to-from)+1).ToList();
    }

    public static List<int> Interpret(string input)
    {
        var result = new List<int>();
        var values = input.Split(Separators);

        string rangePattern = @"(?<range>(?<from>\d+)-(?<to>\d+))";
        var regex = new Regex(rangePattern);

        foreach (string value in values)
        {
            var match = regex.Match(value);
            if (match.Success)
            {
                var from = Parse(match.Groups["from"].Value);
                var to = Parse(match.Groups["to"].Value);
                result.AddRange(Explode(from, to));
            }
            else
            {
                result.Add(Parse(value));
            }
        }

        return result;
    }

    /// <summary>
    /// Split this out to allow custom throw etc
    /// </summary>
    private static int Parse(string value)
    {
        int output;
        var ok = int.TryParse(value, out output);
        if (!ok) throw new FormatException($"Failed to parse '{value}' as an integer");
        return output;
    }
}

and the tests:

    [Test]
    public void ExplodeRange()
    {
        var output = Range.Explode(5, 9);

        Assert.AreEqual(5, output.Count);
        Assert.AreEqual(5, output[0]);
        Assert.AreEqual(6, output[1]);
        Assert.AreEqual(7, output[2]);
        Assert.AreEqual(8, output[3]);
        Assert.AreEqual(9, output[4]);
    }

    [Test]
    public void ExplodeSingle()
    {
        var output = Range.Explode(1, 1);

        Assert.AreEqual(1, output.Count);
        Assert.AreEqual(1, output[0]);
    }

    [Test]
    public void InterpretSimple()
    {
        var output = Range.Interpret("50");
        Assert.AreEqual(1, output.Count);
        Assert.AreEqual(50, output[0]);
    }

    [Test]
    public void InterpretComplex()
    {
        var output = Range.Interpret("1,5-9,14,16,17,20-24");

        Assert.AreEqual(14, output.Count);
        Assert.AreEqual(1, output[0]);
        Assert.AreEqual(5, output[1]);
        Assert.AreEqual(6, output[2]);
        Assert.AreEqual(7, output[3]);
        Assert.AreEqual(8, output[4]);
        Assert.AreEqual(9, output[5]);
        Assert.AreEqual(14, output[6]);
        Assert.AreEqual(16, output[7]);
        Assert.AreEqual(17, output[8]);
        Assert.AreEqual(20, output[9]);
        Assert.AreEqual(21, output[10]);
        Assert.AreEqual(22, output[11]);
        Assert.AreEqual(23, output[12]);
        Assert.AreEqual(24, output[13]);
    }

    [ExpectedException(typeof (FormatException))]
    [Test]
    public void InterpretBad()
    {
        Range.Interpret("powdered toast man");
    }

Answer 5

Write an extension method like this

 public static class NumericExtentions
    {
        public static bool InRange(this int value, int from, int to)
        {
            if (value >= from && value <= to)
                return true;
            return false;
        }

        public static bool InRange(this double value, double from, double to)
        {
            if (value >= from && value <= to)
                return true;
            return false;
        }
    }

and then use it elegantly

if (age.InRange(18, 39))
{ 
//Logic
}

Answer 6

This implementation, inspired by @drharris 's answer, allows you to define proper mathematical interval with values, that can be Inclusive/Exclusive.

/// <summary>The Interval class.</summary>
/// <typeparam name="T">Generic parameter.</typeparam>
public class Interval<T> : IEquatable<Interval<T>>
    where T : IComparable<T>, IEquatable<T>
{
    public Interval()
    { }

    public Interval(IntervalValue<T> minimum, IntervalValue<T> maximum)
    {
        this.Minimum = minimum;
        this.Maximum = maximum;
    }

    /// <summary>Minimum value of the interval.</summary>
    public IntervalValue<T>? Minimum { get; set; }

    /// <summary>Maximum value of the interval.</summary>
    public IntervalValue<T>? Maximum { get; set; }

    /// <summary>Presents the Interval in readable format.</summary>
    /// <returns>String representation of the Interval</returns>
    public override string ToString()
    {
        var min = this.Minimum;
        var max = this.Maximum;
        var sb = new StringBuilder();

        if (min.HasValue)
            sb.AppendFormat(min.Value.ToString(IntervalNotationPosition.Left));
        else
            sb.Append("(-∞");

        sb.Append(',');

        if (max.HasValue)
            sb.AppendFormat(max.Value.ToString(IntervalNotationPosition.Right));
        else
            sb.Append("∞)");

        var result = sb.ToString();

        return result;
    }

    /// <summary>Determines if the interval is valid.</summary>
    /// <returns>True if interval is valid, else false</returns>
    public bool IsValid()
    {
        var min = this.Minimum;
        var max = this.Maximum;

        if (min.HasValue && max.HasValue)
            return min.Value.Value.CompareTo(max.Value.Value) <= 0;

        return true;
    }

    /// <summary>Determines if the provided value is inside the interval.</summary>
    /// <param name="x">The value to test</param>
    /// <returns>True if the value is inside Interval, else false</returns>
    public bool ContainsValue(T x)
    {
        if (x == null)
            throw new ArgumentNullException(nameof(x));

        var min = this.Minimum;
        var max = this.Maximum;
        var isValid = this.IsValid();

        if (!isValid)
            throw new InvalidOperationException("Interval is not valid.");

        bool result = true; // (-∞,∞)

        if (min.HasValue)
        {
            if (min.Value.Type == IntervalValueType.Exclusive)
                result &= min.Value.Value.CompareTo(x) < 0;
            else if (min.Value.Type == IntervalValueType.Inclusive)
                result &= min.Value.Value.CompareTo(x) <= 0;
            else
                throw new NotSupportedException();
        }

        if (max.HasValue)
        {
            if (max.Value.Type == IntervalValueType.Exclusive)
                result &= max.Value.Value.CompareTo(x) > 0;
            else if (max.Value.Type == IntervalValueType.Inclusive)
                result &= max.Value.Value.CompareTo(x) >= 0;
            else
                throw new NotSupportedException();
        }

        return result;
    }

    public bool Equals(Interval<T> other)
    {
        if (other == null)
            return false;

        if (ReferenceEquals(this, other))
            return true;

        return this.Minimum?.Equals(other.Minimum) == true
            && this.Maximum?.Equals(other.Maximum) == true;
    }

    public override bool Equals(object obj)
    {
        return this.Equals(obj as Interval<T>);
    }

    public override int GetHashCode()
    {
        unchecked
        {
            int hash = (int)2166136261;

            hash = hash * 16777619 ^ this.Minimum?.GetHashCode() ?? 0;
            hash = hash * 16777619 ^ this.Maximum?.GetHashCode() ?? 0;

            return hash;
        }
    }
}

public struct IntervalValue<T> : IEquatable<IntervalValue<T>>
    where T : IComparable<T>, IEquatable<T> //, IFormattable
{
    private readonly T value;
    private readonly IntervalValueType type;

    public IntervalValue(T value, IntervalValueType type)
    {
        if (value == null)
            throw new ArgumentNullException(nameof(value));

        this.value = value;
        this.type = type;
    }

    public T Value
    {
        get { return this.value; }
    }

    public IntervalValueType Type
    {
        get { return this.type; }
    }

    public bool Equals(IntervalValue<T> other)
    {
        return this.value.Equals(other.value)
            && this.type == other.type;
    }

    public override bool Equals(object obj)
    {
        return obj is IntervalValue<T> && this.Equals((IntervalValue<T>)obj);
    }

    public override int GetHashCode()
    {
        unchecked
        {
            int hash = (int)2166136261;

            hash = hash * 16777619 ^ this.value.GetHashCode();
            hash = hash * 16777619 ^ this.type.GetHashCode();

            return hash;
        }
    }

    internal string ToString(IntervalNotationPosition position)
    {
        var notation = this.Type.ToString(position);

        switch (position)
        {
            case IntervalNotationPosition.Left:
                return string.Format("{0}{1}", notation, this.Value);

            case IntervalNotationPosition.Right:
                return string.Format("{0}{1}", this.Value, notation);

            default:
                throw new NotSupportedException();
        }
    }
}

internal static class IntervalValueTypeExtensions
{
    public static string ToString(this IntervalValueType type, IntervalNotationPosition position)
    {
        switch (position)
        {
            case IntervalNotationPosition.Left:
                switch (type)
                {
                    case IntervalValueType.Inclusive: return "[";
                    case IntervalValueType.Exclusive: return "(";

                    default:
                        throw new NotSupportedException();
                }

            case IntervalNotationPosition.Right:
                switch (type)
                {
                    case IntervalValueType.Inclusive: return "]";
                    case IntervalValueType.Exclusive: return ")";

                    default:
                        throw new NotSupportedException();
                }
                break;

            default:
                throw new NotSupportedException();
        }
    }
}

public enum IntervalValueType
{
    Inclusive,
    Exclusive
}

public enum IntervalNotationPosition
{
    Left,
    Right
}

Answer 7

Also, a bit of a different tangent here but sometimes ranges are useful only to iterate over them, a bit like it is customary to do in python. In that case, the System.Linq namespace defines a static IEnumerable<int> Range(Int32, Int32) method, which, as the signature suggests,

generates a sequence of integral numbers within a specified range

See the documentation and examples on MSDN

Answer 8

There is a Enumerable.Range method but this one accepts start and count as its parameter. In order for it to work as what you want start and end, the end formula would be end - start + 1

Usage:

Enumerable.Range(start, end - start + 1).ToList()

Answer 9

Since I was also missing intervals in C#, I implemented a fully generic Interval class which can even take care of intervals with more complex types, e.g. an interval between two DateTime's, which involves TimeSpan's during calculations.

An example use case, where a GUI element represents a time interval:

// Mockup of a GUI element and mouse position.
var timeBar = new { X = 100, Width = 200 };
int mouseX = 180;

// Find out which date on the time bar the mouse is positioned on,
// assuming it represents whole of 2014.
var timeRepresentation = new Interval<int>( timeBar.X, timeBar.X + timeBar.Width );
DateTime start = new DateTime( 2014, 1, 1 );
DateTime end = new DateTime( 2014, 12, 31 );
var thisYear = new Interval<DateTime, TimeSpan>( start, end );
DateTime hoverOver = timeRepresentation.Map( mouseX, thisYear );

// If the user clicks, zoom in to this position.
double zoomLevel = 0.5;
double zoomInAt = thisYear.GetPercentageFor( hoverOver );
Interval<DateTime, TimeSpan> zoomed = thisYear.Scale( zoomLevel, zoomInAt );

// Iterate over the interval, e.g. draw labels.
zoomed.EveryStepOf( TimeSpan.FromDays( 1 ), d => DrawLabel( d ) );

For a more extensive representation of the supported functionality check out the unit tests.

Under the covers it uses expression trees to compile type operator operations at runtime, which are cached so there is only a cost the first time the type is initialized.

Answer 10

How about a struct?