public static Optional <TValue> Find <TKey, TValue>(this IDictionary <TKey, TValue> dictionary, TKey key)
{
if (dictionary.TryGetValue(key, out var value))
{
return(Optional.Some(value));
}
return(Optional.None <TValue>());
}
public static Optional <U> Apply <T, U>(this Optional <T> optional, Optional <Func <T, U> > applier)
{
if (optional.HasValue && applier.HasValue)
{
return(Optional.Some(applier.Value(optional.Value)));
}
return(Optional.None <U>());
}
public static Optional <TKey> FindKey <TKey, TValue>(this IDictionary <TKey, TValue> dictionary, Func <TKey, TValue, bool> predicate)
{
foreach (var kvp in dictionary)
{
if (predicate(kvp.Key, kvp.Value))
{
return(Optional.Some(kvp.Key));
}
}
return(Optional.None <TKey>());
}
public static Optional <T> FindValue <T>(this IList <T> list, Func <T, bool> predicate)
{
foreach (var item in list)
{
if (predicate(item))
{
return(Optional.Some(item));
}
}
return(Optional.None <T>());
}
public static Optional <U> Pick <TKey, TValue, U>(this IDictionary <TKey, TValue> dictionary, Func <TKey, TValue, Optional <U> > picker)
{
foreach (var kvp in dictionary)
{
var pickResult = picker(kvp.Key, kvp.Value);
if (pickResult.HasValue)
{
return(pickResult);
}
}
return(Optional.None <U>());
}
public static Optional <U> Pick <T, U>(this IList <T> list, Func <T, Optional <U> > picker)
{
foreach (var item in list)
{
var pickResult = picker(item);
if (pickResult.HasValue)
{
return(pickResult);
}
}
return(Optional.None <U>());
}
public static Optional <T> Filter <T>(this Optional <T> optional, Predicate <T> filter)
{
return(optional.FlatMap(t => filter(t) ? Optional.Some(t) : Optional.None <T>()));
}
public static Optional <U> FlatMap <T, U>(this Optional <T> optional, Func <T, Optional <U> > mapper)
{
return(optional.HasValue ? mapper(optional.Value) : Optional.None <U>());
}
