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I'm not sure how to feel about this:

inline fun Fraction.toThePowerOf(exponent: Fraction): Fraction = Math.pow(this, exponent)

I like it, I think turning prefix functions to infix functions is a good usage of extension methods in C-family languages.

Me too 🙂 Should it be

inline

, though?

I think that’s probably fine, it’s a mathematical operation so I don’t see any issue with it. I’m not sure if I have a good sense for what should be inline vs. not though, since I’m mostly fine with nothing ever being inline.

better performance if is inlined, slightly bigger bytecode

Derp, I was thinking about infix, not inline. I don’t think there’s any reason to inline it, if the JIT thinks it’s worthwhile it will do the inlining.

is JIT a part of the desktop Java SE? I know it's heavily used in Android

yes, it is

The JVM JIT is much better than the Android JIT. If you are concerned about the performance of a long-running application (like a game) I suggest you use the -server flag, which will make the JIT more aggressive about what optimizations it performs. I’ve seen the JVM JIT produce SSE code for vector operations with a debugger attached, for example.

I see!

@benleggiero in this case

inline

does not affect performance since the code of the

toThePowerOf

function is another function

Math.pow

and no operations are performed on the parameters.

In a more complicated case

inline

will worsen the performance because it misleads the JIT

The only valuable use case I see is to use

inline

+

@InlineOnly

do decrease the method count. This is mostly applicable to libraries, not projects

I figured 🙂

Thanks for clarifying! People are always warning me about

inline

fighting JIT and I want to learn just how so I can balance the two

Think about it this way: Java does not have inlining in any form, and JIT is optimized to do Java

very true

hello - i am trying to learn kotlin by rewriting a java android program in it. i have an rxutils class im currently porting over.

can i do better than what you see here?

RxUtil.kt is my first crack at rewriting the RxUtil.java class to use kotlin’s magic

Well first of all I'd bring

LOADING_MESSAGE

back out of global scope, since not all classes need to see it. Maybe put it in an

object RxConstants

or something. Also, why are these functions members of all `Observable`s? What's the idea behind that? Genuinely curious. Other than that looks nice to me. Without being sure how you're using

RxUtils.java

or why you built it, that's the most I can say.

hi @benleggiero thanks for taking a look!

re:

LOADING_MESSAGE

-> wouldn’t making that field private have the same effect?

it would just be available within that file at that point, wouldn’t it?

@benleggiero thanks for asking about the class extensions! What i had realized was a class extension essentially does what

compose

from rxjava does, except built into the language and with less code

(unless of course i am missing something there - new to kotlin !)

i noticed that i could mark them private also, which made me more comfortable using them

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