public void EitherMapRightWhenLeft()
{
bool expected = false;
Either <string, int> either = "10";
Either <string, bool> eitherResult =
EitherModule.MapRight(
_isEven,
either);
bool result = eitherResult.Match(right => right, left => false);
Assert.AreEqual(expected, result);
}
/// <summary>
/// Creates a new <see cref="Either{TLeft, TRight}"/> whose value is the result of applying the given <paramref name="mapping"/> function when <see cref="Either{TLeft, TRight}.IsRight"/>.
/// Otherwise, returns itself.
/// </summary>
/// <typeparam name="TLeft">The type of the left value.</typeparam>
/// <typeparam name="TRight">The type of the right value.</typeparam>
/// <typeparam name="TRightResult">The type of the right value returned by mapping functions</typeparam>
/// <param name="mapping">The function to transform either value when <see cref="Either{TLeft, TRight}.IsRight"/>.</param>
/// <param name="either">the input either.</param>
/// <returns>
/// Returns a new <see cref="Either{TLeft, TRight}"/> whose value is the result of applying the given mapping functions.
/// </returns>
public static Either <TLeft, TRightResult> MapRight <TLeft, TRight, TRightResult>(
this Either <TLeft, TRight> either,
Func <TRight, TRightResult> mapping)
=> EitherModule.MapRight(mapping, either);