Hello everyone! Kotlin null-safety is great. And h...

# library-development

[Luca Piccinelli]

Hello everyone! Kotlin null-safety is great. And having a Result type out-of-the-box is great as well. What I don't like about those features, is that it is not provided a clean way to compose many nulls or many Result.
That's the reason why I came out with Konad library. https://github.com/lucapiccinelli/konad
Instead of composing nulls like the following

val foo: Int? = 1
val bar: String? = "2"
val baz: Float? = 3.0f

fun useThem(x: Int, y: String, z: Float): Int = x + y.toInt() + z.toInt()

val result1: Int? = foo
    ?.let { bar
    ?.let { baz
    ?.let { useThem(foo, bar, baz) } } }

// or

val result2: Int? = if(foo != null && bar != null && baz != null) 
    useThem(foo, bar, baz) 
    else null

you have an API like

val result: Int? = ::useThem.curry() 
    .on(foo.maybe) 
    .on(bar.maybe) 
    .on(baz.maybe)
    .nullable

or even with error messages

val result: Result<Int> = ::useThem.curry() 
    .on(foo.ifNull("Foo should not be null")) 
    .on(bar.ifNull("Bar should not be null")) 
    .on(baz.ifNull("Baz should not be null"))
    .result