/// <summary>
/// If <paramref name="a"/> has value, applies <paramref name="fn"/> to it, and if the result also has value, calls <paramref name="composer"/> on both values
/// (original and fn-call-resulted), and returns the <paramref name="composer"/>-call result, wrapped in Maybe. Otherwise returns nothing.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <typeparam name="TTempResult"></typeparam>
/// <typeparam name="TResult"></typeparam>
/// <param name="a"></param>
/// <param name="fn"></param>
/// <param name="composer"></param>
/// <returns></returns>
public static Maybe <TResult> SelectMaybe <T, TTempResult, TResult>(this Maybe <T> a, Func <T, Maybe <TTempResult> > fn, Func <T, TTempResult, TResult> composer)
{
return(a.SelectMany(fn, composer));
}
/// <summary>
/// If <paramref name="a"/> has value, applies <paramref name="fn"/> to it, and if the result also has value, calls <paramref name="composer"/> on both values
/// (original and fn-call-resulted), and returns the <paramref name="composer"/>-call result, wrapped in Maybe. Otherwise returns nothing.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <typeparam name="TTempResult"></typeparam>
/// <typeparam name="TResult"></typeparam>
/// <param name="a"></param>
/// <param name="fn"></param>
/// <param name="composer"></param>
/// <returns></returns>
public static Maybe <TResult> SelectMany <T, TTempResult, TResult>(this Maybe <T> a, Func <T, Maybe <TTempResult> > fn, Func <T, TTempResult, TResult> composer)
{
return(a.SelectMany(x => fn(x).SelectMany(y => composer(x, y).ToMaybe())));
}
/// <summary>
/// If <paramref name="a"/> has value, applies <paramref name="fn"/> to it and returns, otherwise returns Nothing. Alias for SelectMany.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <typeparam name="TR"></typeparam>
/// <param name="a"></param>
/// <param name="fn"></param>
/// <returns></returns>
public static Maybe <TR> SelectMaybe <T, TR>(this Maybe <T> a, Func <T, Maybe <TR> > fn)
{
return(a.SelectMany(fn));
}