That’s exactly what I was writing, you beat me to it simple smile

You could also

reduce

although since the base is given,

fold

might make more sense here

map and filter are already second nature for me but fold and reduce is something I need to think of more often

= segments.reduce { a,b -> File(a,b).path }

(although this produces a

String

, need to wrap it in a

File

(actually this code doesn’t use

base

so it’s buggy but you get the idea)

fold is clearly better in this case

There’s also

= File(base, segments.joinToString(File.separator))

File

will remove double separators, right?

Probably not, might need to

normalize()

(or just ignore it since

File

doesn’t mind AFAIR)

javadoc of

java.io.File#fixSlashes

says "Removes duplicate adjacent slashes and any trailing slash."

it's invoked in the constructor

do I need to import anything to use

compareBy

?

I believe yes

what's the package name?

it's in

kotlin.comparisons

it's not imported by default anymore starting with one of the RCs

ah, thought there were other parts before

kotlin

, all working now, thanks

how about this in Kotlin: https://gist.github.com/maxd/8f967002343865dd40a7? Is it totally agains kotlin ideology ?

kotlin doesn't have much of an ideology. i'd say though, that this is not especially readable.

it's the sort of questionable use of operator overloading that gives the feature a bad name, I think. sorry.

why the reference equality check?

==

should be enough

other than that, I think it's not too bad.

too bad it can throw, though

and why do you need reification?

operator fun <L : Any, R : Any> KClass<L>.compareTo(other: KClass<R>) = when {
    this == other -> 0
    this.java.isAssignableFrom(other.java) -> -1
    other.java.isAssignableFrom(this.java) -> 1
    else -> throw IllegalArgumentException("Classes doesn't have common hierarchy.")
}

works just as well

also, you can throw away the generics, since you don't use them anyway:

operator fun  KClass<*>.compareTo(other: KClass<*>) = when {
    this == other -> 0
    this.java.isAssignableFrom(other.java) -> -1
    other.java.isAssignableFrom(this.java) -> 1
    else -> throw IllegalArgumentException("Classes doesn't have common hierarchy.")
}

@kirillrakhman: totally agree.

this was a prototype \ demonstration of the concept

I am more interested in the feedbag on the syntax inself

well, you kinda break the contract of

compareTo

by throwing