public void EitherFoldBackRightWhenLeft() { int state = 10; int expected = 10; Either <string, int> either = "10"; int result = EitherModule.FoldBackRight( (right, _state) => right + _state, either, state); Assert.AreEqual(expected, result); }
/// <summary> /// Creates a new <typeparamref name="TState"/> value by applying the given <paramref name="folder"/> function /// to <see cref="Either{TLeft, TRight}"/> value and <paramref name="state"/> when the <paramref name="either"/> <see cref="Either{TLeft, TRight}.IsRight"/>. /// Otherwise, returns the <paramref name="state"/>. /// </summary> /// <typeparam name="TLeft">The type of the left value.</typeparam> /// <typeparam name="TRight">The type of the right value.</typeparam> /// <typeparam name="TState">The type of initial and final states</typeparam> /// <param name="folder">The function to transform either value from the input <paramref name="either"/> to a new state value.</param> /// <param name="state">The initial state.</param> /// <param name="either">the input either.</param> /// <returns> /// Returns a new <typeparamref name="TState"/> value by applying the given <paramref name="folder"/> function /// to <see cref="Either{TLeft, TRight}"/> value and <paramref name="state"/> when the <paramref name="either"/> <see cref="Either{TLeft, TRight}.IsRight"/>. /// Otherwise, returns the input <paramref name="either"/>. /// </returns> public static TState FoldBackRight <TLeft, TRight, TState>(this Either <TLeft, TRight> either, Func <TRight, TState, TState> folder, TState state) => EitherModule.FoldBackRight(folder, either, state);