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Monads/Maybe monad: Difference between revisions
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</pre>
=={{header|C sharp|C#}}==
<lang csharp>using System;
namespace RosettaMaybe
{
// courtesy of https://www.dotnetcurry.com/patterns-practices/1510/maybe-monad-csharp
public abstract class Maybe<T>
{
public sealed class Some : Maybe<T>
{
public Some(T value) => Value = value;
public T Value { get; }
}
public sealed class None : Maybe<T> { }
}
class Program
{
static Maybe<double> MonadicSquareRoot(double x)
{
if (x >= 0)
{
return new Maybe<double>.Some(Math.Sqrt(x));
}
else
{
return new Maybe<double>.None();
}
}
static void Main(string[] args)
{
foreach (double x in new double[] { 4.0D, 8.0D, -15.0D, 16.23D, -42 })
{
Maybe<double> maybe = MonadicSquareRoot(x);
if (maybe is Maybe<double>.Some some)
{
Console.WriteLine($"The square root of {x} is " + some.Value);
}
else
{
Console.WriteLine($"Square root of {x} is undefined.");
}
}
}
}
}</lang>
=={{header|C++}}==
<lang cpp>#include <iostream>
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