using System;

using System.Numerics;

using System.Linq;

​

using NUnit.Framework;

​

//https://stackoverflow.com/questions/79140689/convert-inumbert-in-c-sharp-to-float-net-7-or-newer

​

public static class Interpolation

{

    public static T LinearBetween<T>((T x1, T y1) a, (T x2, T y2) b, T x) where T : INumber<T> =>

        LinearBetween<T, double>(a, b, x); // TODO: decide whether float is precise enough

​

    public static T LinearBetween<T, TFloat>((T x1, T y1) a, (T x2, T y2) b, T x) 

        where T : INumber<T>, INumberBase<T>

        where TFloat : IFloatingPoint<TFloat>

    {

        if (NumericTypeInformation<T>.IsBinaryInteger)

        {

            // An integer type.  Convert to the preferred float format, perform the calculation, then round at the very end.

            var floatResult =  LinearBetweenUnconverted(

                (TFloat.CreateChecked(a.x1), TFloat.CreateChecked(a.y1)),

                (TFloat.CreateChecked(b.x2), TFloat.CreateChecked(b.y2)),

                TFloat.CreateChecked(x));

            var rounded = TFloat.Round(floatResult, MidpointRounding.ToEven); // TODO: choose your preferred MidpointRounding

            return T.CreateChecked(rounded);

        }

        else

        {

            // Not an integer type.  Perform the calculation directly.

            return LinearBetweenUnconverted(a, b, x);

        }

    }

​

    static T LinearBetweenUnconverted<T>((T x1, T y1) a, (T x2, T y2) b, T x) where T : INumber<T>

    {

        var m = (b.y2 - a.y1) / (b.x2 - a.x1);

        var n = b.y2 - m * b.x2;

​

        return (x * m + n);

    }

}

​

// Generic class to static cache type information about a given numeric type.

public static class NumericTypeInformation<TNumber> where TNumber : INumberBase<TNumber>

{

    readonly static Lazy<bool> isBinaryInteger = new Lazy<bool>(

        () => typeof(TNumber)

              .GetInterfaces()

              .Where(i => i.IsGenericType)

              .Select(i => i.GetGenericTypeDefinition())

              .Any(i => i == typeof(IBinaryInteger<>)));

​

    public static bool IsBinaryInteger => isBinaryInteger.Value;

}

​

​

public static class Extensions

{

    public static int RoundToInt(this float value)

    {

        return (int)Math.Round(value);

    }

​

    public static void DumpIt(this object toDump)

    {

        Console.WriteLine(toDump);

    }

}

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Environment version: {0} ({1}), {2}.\n", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , Environment.Version, Environment.OSVersion);

        Interpolation.LinearBetween((0, 5), (10, 3), 7).DumpIt();

        //Interpolation.LinearBetweenUnconverted((0, 5), (10, 3), 7).DumpIt();

        Interpolation.LinearBetween((0.0f, 5), (10, 3), 7).RoundToInt().DumpIt();

        Assert.That(Interpolation.LinearBetween((0, 5), (10, 3), 7) == Interpolation.LinearBetween((0.0f, 5), (10, 3), 7).RoundToInt());

    }

}

​

​