kotlinlang #stdlib

fun Int.reinterpretAsFloat(): Float = java.lang.Float.intBitsToFloat(this)
fun Float.reinterpretAsInt(): Int = java.lang.Float.floatToIntBits(this)

fun Long.reinterpretAsDouble(): Double = java.lang.Double.longBitsToDouble(this)
fun Double.reinterpretAsLong(): Long = java.lang.Double.doubleToLongBits(this)

They are useful for binary serialization and for some floating point hacks/introspection. As far as I know it has been already implemented but with different API. Using toBits and Companion.fromBits to both Float and Double. Not sure which one is better. But I wanted to suggest this anyway :)

trevjones

09/28/2017, 9:05 PM

In rx there is a

.toMultimap

operator that takes a key selector function. is there a kotlin stdlib equivalent?

09/28/2017, 9:20 PM

groupBy

trevjones

09/28/2017, 9:20 PM

ty sir

gaetan

09/29/2017, 8:10 AM

Another point on the 1.2 version on the stlib. You made the choice of introducing

log(double, double)

function which is a generic version of

log

allowing to call log with any base. In real life, I think that the 3 classical logs (natural, base 10, base 2) are enough for 99,9% of uses. By introducing this function, you change the conventions of having log representing the natural log, replacing it by

ln(double)

. Even, if it’s more correct I’m not sure that kotlin have to fix java and javascript. If someone need the generic version of log he could implement it in his code.

beholder

09/30/2017, 11:52 AM

If I have KClass for companion object, can I get KClass for its base? (besides name manipulation)

dmcg

09/30/2017, 12:59 PM

I've been looking at the performance of mapping over lists for my KotlinConf session. Is there any specialised version of

List.map

? If not, why not, given the performance that could be gained?

kirillrakhman

09/30/2017, 1:11 PM

relevant: https://youtrack.jetbrains.com/issue/KT-9607

dmcg

09/30/2017, 1:19 PM

Excellent, thank you

dmcg

09/30/2017, 1:43 PM

~I see iteration by index as ~~20 x faster than iterator for 10000 elements in linked list. Given that almost every List will be an ArrayList, and you could specialise for MutableList, I'm not (yet) convinced by the argument~~

dmcg

10/01/2017, 1:36 PM

OK, found the bug. Retracting those results

dmcg

10/01/2017, 9:34 PM

Has anyone tried building iteration on Iterarable.spliterator()? (I think) I'm getting promising results.

👍 1

dmcg

10/01/2017, 9:35 PM

https://github.com/dmcg/kostings/blob/806f6189dc1e838caaf8201b79e4ddb83c355174/src/main/java/costOfKotlin/mapping/KotlinMapping.kt

10/09/2017, 4:26 PM

is there a way to compare the contents of a list inside a comparator chain?

10/09/2017, 4:26 PM

for example, say you're writing a comparator for

data class Names(val names: List<String>)

karelpeeters

10/09/2017, 4:28 PM

What do you want to compare?

10/09/2017, 4:28 PM

the contents of a list

10/09/2017, 4:33 PM

i mean i can write my own comparator that basically does a zip and early returns on first difference, but i'm surprised to not find something to assist

orangy

10/09/2017, 4:51 PM

Doesn’t it just work?

10/09/2017, 4:51 PM

a List isn't Comparable

orangy

10/09/2017, 4:52 PM

Ah, missed the comparator part, sorry

10/09/2017, 4:54 PM

yeah my real example is like

val foo: String, val bars: List<String>, val baz: String

so I have

compareBy(MyType::foo).thenComparing(MyType::bars, bigCustomIterableCompratorFactory()).thenBy(MyType::baz)

10/09/2017, 4:54 PM

i expected some way to get a comparator for an iterable of comparables without having to write my own

bigCustomIterableCompratorFactory

function or maybe some way of specifying that I want that property compared by its iterable values

10/09/2017, 4:57 PM

hard to Google for since every result is about sorting a list using a comparator

karelpeeters

10/09/2017, 4:58 PM

Well if it's not in

comparators.kt

nor defined on the

List

Iterable

interfaces it probably just doesn't exist.

10/09/2017, 5:00 PM

i don't need a single function that does exactly what i need. usually there are idioms which apply the capabilities to more advanced use cases such as over a collection

10/09/2017, 5:00 PM

but i don't see any of those being possible either