public static Fallible <IEnumerable <TResult> > Zip <T1, T2, TResult>(
IEnumerable <T1> first,
IEnumerable <T2> second,
Func <T1, T2, Fallible <TResult> > resultSelector)
=> Fallible.Collect(first.Zip(second, resultSelector));
public static Fallible <IEnumerable <TResult> > Map <T, TResult>(
IEnumerable <T> source,
Func <T, Fallible <TResult> > selector)
=> Fallible.Collect(source.Select(selector));