Trarizon.Library.Functional 1.0.4

Trarizon.Library.Functional

Provides utilities for functional programming (Monads)

Monads

Optional<>, Result<,>, Either<,> are available, a non-generic type with same name is provided as factory(eg: Optional for Optional<T>, etc.).

All monads are value type

Optional & RefOptional

Use Optional.Of / Optional.None / Optional<T>.None to create a Optional<T> with or without value. We provider Optional.Create/OfNotNull/OfPredicate to help you quickly create a Optional<T> according to some predicate

With allows ref struct in .NET9, RefOptional<T> is provided as a Optional<T> for ref struct and has almost same functions with Optional<T>. You can use RefOptional.Of etc. to create RefOptional<T>, if your language version is C#14 or later, you can just use Optional.Of, and RefOptional<T> will be created if argument is ref struct.

Optional<T> and RefOptional<T> are implicitly convertable to each other, you can also use AsRef() and AsDeref() to convert between Optional<T> and RefOptional<T>

Optional<T> is implicited castable from a value

Optional<T> has following members to access data

• HasValue
• Value : This property won't throw if this is None
• GetValueOrThrow()
• GetValueOrDefault(), GetValueOrDefault(T)
• TryGetValue(out T)
• GetValueRefOrDefaultRef()

Optional<T> has following members to chain

• operator | or operator ||
• Or()
• Cast<TResult>() so you can cast it to its interfaces of base type
• Match() return TResult or void
  • MatchValue() and MatchNone
• Select() map value
• Bind() map value to Optional<TResult>
  • SelectManay() is also provided, so you can use linq expression to do this
• Zip()
• Where() filter
• ToNullable() convert to Nullable<T>

Optional<T> has some methods related to IEnumerable<T>

• IEnumerable<Optional<T>>.Collect(): Optional<IEnumerable<T>> returns the sequence if all optionals has value, else return None
• IEnumerable<T>.WhereSelect(Func<T, Optional<TResult>>) : IEnumerable<TRsult> Linq Where and Select
• IEnumerable<Optional<T>>.WhereHasValue() : IEnumerable<T> returns sequence contains values

You may notice that Optional.None returns a Optional.NoneBuilder, Result.Success() returns a Result.SuccessBuilder<T> etc. They can be implicitly converted to or use Build() to create a monad type.

I use this so that when I want to create a Optional.None, I don't have to specify the type of value like Optional.None<T>(), this works better on Result<T, TError>, as you can use Result.Success(1) to create a Success rather than Result.Success<int, string>(1), C# force you to write all type arguments if compiler don't know.

Also, all types are designed in value type, so I should avoid boxing and cannot use inheritance

Result