public void EitherToOptionLeftWhenLeft()
{
string expected = "Hello World";
Either <string, int> either = expected;
Option <string> optionResult =
EitherModule.ToOptionLeft(either);
string result = optionResult.Match(value => value, () => string.Empty);
Assert.AreEqual(expected, result);
}
/// <summary>
/// Convert the <see cref="Either{TLeft, TRight}"/> to a <see cref="Option{T}"/> where T is <typeparamref name="TLeft"/>.
/// </summary>
/// <typeparam name="TLeft">The type of the left value.</typeparam>
/// <typeparam name="TRight">The type of the right value.</typeparam>
/// <param name="either">The input either.</param>
/// <returns>
/// Returns an <see cref="Option{T}"/> where T is <typeparamref name="TLeft"/>.
/// The option value state is <see cref="Option{T}.Some(T)"/> when <paramref name="either"/> <see cref="Either{TLeft, TRight}.IsLeft"/>, otherwise is <see cref="Option{T}.None"/>
/// </returns>
public static Option <TLeft> ToOptionLeft <TLeft, TRight>(this Either <TLeft, TRight> either)
=> EitherModule.ToOptionLeft(either);
