public Maybe <TResult> SelectMany <TMiddle, TResult>(
Func <T, Maybe <TMiddle> > selector,
Func <T, TMiddle, TResult> resultSelector)
{
if (selector is null)
{
throw new Anexn(nameof(selector));
}
if (resultSelector is null)
{
throw new Anexn(nameof(resultSelector));
}
if (!_isSome)
{
return(Maybe <TResult> .None);
}
Maybe <TMiddle> middle = selector(_value);
if (!middle._isSome)
{
return(Maybe <TResult> .None);
}
return(Maybe.Of(resultSelector(_value, middle._value)));
}
public Maybe <TResult> Select <TResult>(Func <T, TResult> selector)
{
if (selector is null)
{
throw new Anexn(nameof(selector));
}
return(_isSome ? Maybe.Of(selector(_value)) : Maybe <TResult> .None);
}
public static async Task <Maybe <TResult> > SelectAsync <T, TResult>(
this Maybe <T> @this,
Func <T, Task <TResult> > selector,
bool continueOnCapturedContext)
{
if (selector is null)
{
throw new Anexn(nameof(selector));
}
return(@this.TryGetValue(out T? value)
? Maybe.Of(await selector(value).ConfigureAwait(continueOnCapturedContext))
: Maybe <TResult> .None);
}
private static Maybe <TResult> GroupJoinImpl <TOuter, TInner, TKey, TResult>(
Maybe <TOuter> outer,
Maybe <TInner> inner,
Func <TOuter, TKey> outerKeySelector,
Func <TInner, TKey> innerKeySelector,
Func <TOuter, Maybe <TInner>, TResult> resultSelector,
IEqualityComparer <TKey> comparer)
{
if (outer.TryGetValue(out TOuter? x) && inner.TryGetValue(out TInner? y))
{
TKey outerKey = outerKeySelector(x);
TKey innerKey = innerKeySelector(y);
if (comparer.Equals(outerKey, innerKey))
{
return(Maybe.Of(resultSelector(x, inner)));
}
}
return(Maybe <TResult> .None);
}
private async Task <Maybe <TResult> > SelectAsyncImpl <TResult>(
Func <T, Task <TResult> > selector)
{
return(_isSome ? Maybe.Of(await selector(_value).ConfigureAwait(false))
: Maybe <TResult> .None);
}