SelectMany <TEnv, TFirst, TSecond, TResult>(
this IReader <TEnv, TFirst> reader,
Func <TFirst, IReader <TEnv, TSecond> > secondSelector,
Func <TFirst, TSecond, TResult> resultSelector)
{
if (reader == null)
{
throw new ArgumentNullException(nameof(reader));
}
if (secondSelector == null)
{
throw new ArgumentNullException(nameof(secondSelector));
}
if (resultSelector == null)
{
throw new ArgumentNullException(nameof(resultSelector));
}
return(reader.Bind(x => secondSelector(x).Map(y => resultSelector(x, y))));
}
