Using Arrow.Either in Kotlin

Readme.md

Use typealiases to make something more significant than Left, Right, .a and .b

Main.kt

typealias Result<A> = Either<Exception,A>
typealias Err = Either.Left<Exception>
typealias Ok<A> = Either.Right<A>

fun <T> Result<T>.value(): T? {
    when (this) {
        is Ok -> return this.b
        is Err -> return null
    }
}

fun <T> Result<T>.error(): Exception? {
    when (this) {
        is Err -> return this.a
        is Ok -> return null
    }
}
    
    
// Temp code to test Either
val result1: Result<Int> = Err(InternalErrorException("Something went wrong"))

when (result1) {
    is Err -> println("result1.a ${result1.a}")
    is Ok -> println("result1.b ${result1.b}")
}

val a = result1.exists { it < 4 }
val b = result1.exists { it > 4 }
println("result 1 < 4 $a")
println("result 1 > 4 $b")

result1.map { println("result1 map $it")}
result1.mapLeft { println("result1 mapLeft $it")}

println("result1.value ${result1.value()}")
println("result1.error ${result1.error()}")


val result2: Result<Int> = Ok(5)
when (result2) {
    is Err -> println("result2.a ${result2.a}")
    is Ok-> println("result2.b ${result2.b}")
}

println("result 2 < 4 ${result2.exists { it < 4 }}")
println("result 2 > 4 ${result2.exists { it > 4 }}")

result2.map { println("result2 map $it")}
result2.mapLeft { println("result2 mapLeft $it")}

println("result2.value ${result2.value()}")
println("result2.error ${result2.error()}")