ktuples

Tuple and variant types for kotlin

Warning: generated code inside!

Ever wondered why Kotlin have only two tuple types (Pair and Triple)? Because you usually don't need more. If you really do, use this library. There are two basic concepts available -- Tuples and Variants

Tuples

This lib provides you with types Tuple0, Tuple1, Tuple2 and so on (up to Tuple7 by default) of uniform heterogeneous collections of fixed sizes that works the way they are supposed to work.

There are some additional helper functions and utility constructs available, but the basics are as simple as that: a number of standard kotlin data classes ready to use with any types you want.

Should you use these types to handle your specific cases? Nah. Just roll up your own data class. Kotlin is awesome at that. These are mostly useful when you want to be as generic as possible or the name of the type you would make doesn't make any sense.

All the tuples in this library are immutable. We may add MutableTuple$N types for mutable usecases in the future.

Variants

This lib provides you with types EitherOf2, EitherOf3, EitherOf4 and so on (up to EitherOf7 by default) of generic tagged unions that may contain one of several different types that are represented by types Variant0, Variant1, Variant2 (up to Variant7 by default). Kotlin type system handles the rest (say, Variant2(4) is not a valid value of type EitherOf2<Int, String> or EitherOf3<Int, Double, String>, but it a valid value of type EitherOf3<String, Double, Int>). Values are always boxed, so beware.

As for tuples, when in doubt, roll up your own hierarchy of data classes: these are for generic use mostly.

Another nice Kotlin feature is that you get exhaustive when matching for free:

val x: EitherOf3<Int, Double, String> = ...
when(x) {
    is Variant0 -> functionOfInt(x.value) // x.value is Int
    is Variant1 -> functionOfDouble(x.value) // x.value is Double
    is Variant2 -> functionOfString(x.value) // x.value is String
    // you don't need an else here!~
}

Misc

There are other experimental features in this library that wait to be documented.