Learn Kotlin in Y Minutes • Hacker News Board

Re: Learn Kotlin in Y Minutes

#31

Post by torinmr » Thu, May 18, 2017, 6:13 PM UTC

betatest wrote: post #23

softawre wrote: post #8

Earlier quoted context omitted.

Deservedly so. It is a great language, and it's backed by the ultra-power JVM. You can use a hipster language with great features and still use JodaTime and maven and all the enterprise stuff that just works.

What exactly make it a great language? What are the advantages compared to Java? I search for it but couldn't find any simple answer to that question. The fact that things are shorter to declare doesn't make it better. It makes it less readable.

I haven't used Kotlin, but glancing over their comparison page the one that jumped out to me was that it (almost) eliminates the possibility of null pointer exceptions: https://kotlinlang.org/docs/reference/null-safety.html

Re: Learn Kotlin in Y Minutes

#32

Post by vnglst » Thu, May 18, 2017, 6:15 PM UTC

coldpizza wrote: post #28

> Declaring values is done using either "var" or "val". "val" declarations cannot be reassigned, whereas "vars" can. I wonder why they decided on these very mistakable names. Why not const/constant/cons/whatever else just as long it's distinguishable from each other?

I'm guessing here: With const there's always the disccusion about consts not being constant, e.g. when referencing an array or object (reference itself is constant). With "val" you don't have that confusion?

Re: Learn Kotlin in Y Minutes

#33

Post by wavefunction » Thu, May 18, 2017, 6:16 PM UTC

coldpizza wrote: post #28

> Declaring values is done using either "var" or "val". "val" declarations cannot be reassigned, whereas "vars" can. I wonder why they decided on these very mistakable names. Why not const/constant/cons/whatever else just as long it's distinguishable from each other?

With an IDE you could apply different highlighting styles to the two to minimize confusion.

Re: Learn Kotlin in Y Minutes

#34

Post by mattnewton » Thu, May 18, 2017, 6:18 PM UTC

vnglst wrote: post #32

coldpizza wrote: post #28

> Declaring values is done using either "var" or "val". "val" declarations cannot be reassigned, whereas "vars" can. I wonder why they decided on these very mistakable names. Why not const/constant/cons/whatever else just as long it's distinguishable from each other?

I'm guessing here: With const there's always the disccusion about consts not being constant, e.g. when referencing an array or object (reference itself is constant). With "val" you don't have that confusion?

But why not let? Or any word that doesn't start with "va"?

Re: Learn Kotlin in Y Minutes

#35

Post by namelezz » Thu, May 18, 2017, 6:18 PM UTC

coldpizza wrote: post #28

> Declaring values is done using either "var" or "val". "val" declarations cannot be reassigned, whereas "vars" can. I wonder why they decided on these very mistakable names. Why not const/constant/cons/whatever else just as long it's distinguishable from each other?

var = variable (can vary/change)

val = value (constant)

What can be mistaken?

Re: Learn Kotlin in Y Minutes

#36

Post by k__ » Thu, May 18, 2017, 6:18 PM UTC

I have to damit, I wish Ceylon would have won, hehe.

Re: Learn Kotlin in Y Minutes

#37

Post by kodablah » Thu, May 18, 2017, 6:19 PM UTC

coldpizza wrote: post #28

> Declaring values is done using either "var" or "val". "val" declarations cannot be reassigned, whereas "vars" can. I wonder why they decided on these very mistakable names. Why not const/constant/cons/whatever else just as long it's distinguishable from each other?

Kotlin as a language has expectations on IDE capabilities. I doubt the problem of accidentally typing "r" instead of "l" at the end of a keyword is as prevalent as someone typing "var" instead of "const" and not coming back to make it immutable. A quality compiler can warn about an unmutated mutable variable which solves all problems.

Remember recently on the Java mailing list there was a lot of bikeshedding concerning this point. I don't think it matters near as much as the discussion surrounding it thinks.

Oh, and finally, "const" has a specific meaning: compile time constants.

Re: Learn Kotlin in Y Minutes

#38

Post by sushisource » Thu, May 18, 2017, 6:19 PM UTC

coldpizza wrote: post #28

> Declaring values is done using either "var" or "val". "val" declarations cannot be reassigned, whereas "vars" can. I wonder why they decided on these very mistakable names. Why not const/constant/cons/whatever else just as long it's distinguishable from each other?

Probably because that's what scala does

Re: Learn Kotlin in Y Minutes

#39

Post by asadmshah » Thu, May 18, 2017, 6:20 PM UTC

seanalltogether wrote: post #24

Does it have an equivalent to Swifts if let clause? if let person = selection?.organization?.owner { setTitle(person.name) setImage(person.image) }

Yes.

    val person = selection?.organization?.owner?.let {
        setTitle(it.name)
        setImage(it.image)
        it
    }

Re: Learn Kotlin in Y Minutes

#40

Post by itp » Thu, May 18, 2017, 6:20 PM UTC

betatest wrote: post #23

softawre wrote: post #8

Earlier quoted context omitted.

Deservedly so. It is a great language, and it's backed by the ultra-power JVM. You can use a hipster language with great features and still use JodaTime and maven and all the enterprise stuff that just works.

What exactly make it a great language? What are the advantages compared to Java? I search for it but couldn't find any simple answer to that question. The fact that things are shorter to declare doesn't make it better. It makes it less readable.

For advantages (and some disadvantages!) compared to Java, I'd start with https://kotlinlang.org/docs/reference/comparison-to-java.htm....