Question

I have a loop which loops up to 20.

I am using C# 4.0 and LINQ (Where necessary). What’s a good way to say

"if i > 3 && < 5"

but for various bands (eg between 3 and 5, 6, and 8, etc), without loads of if statements in the loops?

Thanks

Answer 1

If you just want to simplify syntax, you could write an extension method:

public static bool IsBetween(this int num, int exclusiveLowerBound, int exclusiveUpperBound)
{
    return num > exclusiveLowerBound && num < exclusiveUpperBound;
}

Of course, it is debatable if i.IsBetween(3, 5) really is cleaner than the sample you have provided.

If really you are dealing with “various bands”, you could use the efficient Interval Tree data-structure. If performance is not an issue, you could just write a simple class yourself:

public class NumRange
{
    public int ExclusiveLowerBound { get; private set; }
    public int ExclusiveUpperBound { get; private set; }

    public int Size
    {
        get
        {
            return ExclusiveUpperBound - ExclusiveLowerBound;
        }
    }

    public NumRange(int boundary1, int boundary2)
    {
        ExclusiveLowerBound = Math.Min(boundary1, boundary2);
        ExclusiveUpperBound = Math.Max(boundary1, boundary2);
    }

    public bool Contains(int num)
    {
        return num > ExclusiveLowerBound && num < ExclusiveUpperBound;
    }

}

This will allow you to write code like:

var rangeToComment = new Dictionary<NumRange, string>
{
    {new NumRange(3,5), "The number 4."},
    {new NumRange(0, 10),"Single digit natural numbers"},
    {new NumRange(int.MinValue,int.MaxValue),"Integers"}
};

foreach (int number in Enumerable.Range(0, 100))
{
    var tightestRange = rangeToComment.Where(kvp => kvp.Key.Contains(number))
                                      .OrderBy(kvp => kvp.Key.Size)
                                      .First();
    Console.WriteLine("{0}: {1}", number, tightestRange.Value);
}