Determine if a number falls within a specified set of ranges

Question

I\'m looking for a fluent way of determining if a number falls within a specified set of ranges. My current code looks something like this:

int x = 500; // Could         


        

Answer 1

In Pascal (Delphi) you have the following statement:

if x in [40..80] then
begin
end

So if a value x falls in that range you execute your command. I was looking for the C# equivalent to this but can't find something as simple and 'elegant' as this.

This if in() then statement accepts strings, bytes, etc.

Answer 2

class Range { 

    public Range(int x, int y) {
        X = x;
        Y = y;
    }

    public int X { get; set; }
    public int Y { get; set; }
}

var ranges = new List<Range>();
ranges.Add(new Range(4199,6800));
ranges.Add(new Range(6999,8200));
ranges.Add(new Range(9999,10100));
ranges.Add(new Range(10999,11100));
ranges.Add(new Range(11999,12100));

bool inRange = ranges.Count(r => x >= r.X && x <= r.Y) > 0;
//or -- Based on Jons recommendation
bool inRange = ranges.Any(r => x >= r.X && x <= r.Y);

Answer 3

Define a Range type, then create a set of ranges and an extension method to see whether a value lies in any of the ranges. Then instead of hard-coding the values, you can create a collection of ranges and perhaps some individual ranges, giving them useful names to explain why you're interested in them:

static readonly Range InvalidUser = new Range(100, 200);
static readonly Range MilkTooHot = new Range (300, 400);

static readonly IEnumerable<Range> Errors =
    new List<Range> { InvalidUser, MilkTooHot };

...

// Normal LINQ (where Range defines a Contains method)
if (Errors.Any(range => range.Contains(statusCode))
// or (extension method on int)
if (statusCode.InAny(Errors))
// or (extension methods on IEnumerable<Range>)
if (Errors.Any(statusCode))

You may be interested in the generic Range type which is part of MiscUtil. It allows for iteration in a simple way as well:

foreach (DateTime date in 19.June(1976).To(25.December(2005)).Step(1.Days()))
{
    // etc
}

(Obviously that's also using some DateTime/TimeSpan-related extension methods, but you get the idea.)

Answer 4

if you need to iterate over the value pairs at some point, I suggest you capture the maximum lower value and the minimum upper value as you do into variables and do:

if ( x>max_lower && x <min_upper)
{
    // More awesome code

}

Answer 5

LINQ approach :

Add the reference:

using System.Linq;

        /// <summary>
        /// Test to see if value is in specified range.
        /// </summary>
        /// <param name="aStart">int</param>
        /// <param name="aEnd">int</param>
        /// <param name="aValueToTest">int</param>
        /// <returns>bool</returns>
        public static bool CheckValueInRange(int aStart, int aEnd, int aValueToTest)
        {
            // check value in range...
            bool ValueInRange = Enumerable.Range(aStart, aEnd).Contains(aValueToTest);
            // return value...
            return ValueInRange;
        }

Answer 6

Extension methods?

bool Between(this int value, int left, int right)
{ 
   return value > left && value < right; 
}

if(x.Between(4199, 6800) || x.Between(6999, 8200) || ...)

You can also do this awful hack:

bool Between(this int value, params int[] values)
{
    // Should be even number of items
    Debug.Assert(values.Length % 2 == 0); 

    for(int i = 0; i < values.Length; i += 2)
        if(!value.Between(values[i], values[i + 1])
            return false;

    return true;
}

if(x.Between(4199, 6800, 6999, 8200, ...)

Awful hack, improved:

class Range
{
    int Left { get; set; }
    int Right { get; set; }

    // Constructors, etc.
}

Range R(int left, int right)
{
    return new Range(left, right)
}

bool Between(this int value, params Range[] ranges)
{
    for(int i = 0; i < ranges.Length; ++i)
        if(value > ranges[i].Left && value < ranges[i].Right)
            return true;

    return false;
}

if(x.Between(R(4199, 6800), R(6999, 8200), ...))

Or, better yet (this does not allow duplicate lower bounds):

bool Between(this int value, Dictionary<int, int> ranges)
{
    // Basically iterate over Key-Value pairs and check if value falls within that range
}

if(x.Between({ { 4199, 6800 }, { 6999, 8200 }, ... }