kotlinlang #stdlib

Join the conversation Join Slack

Channels

100daysofcode

100daysofkotlin

androidgithubprojects

cincinnati-user-group

competitive-programming

event21-community-content

java-to-kotlin-refactoring

jvm-ir-backend-feedback

kotlin-multiplatform-contest

kotlinultimatechallenge

myndocs-oauth2-server

naming

navigation-architecture-component

practical-functional-programming

proguard

prozis-android-backup

refactoring-to-kotlin

russian-kotlinasfirst

skia-wasm-interop-temp

stayhungrystayfoolish

swagger-gradle-codegen

tricity-kotlin-user-group

stdlib

chalup

04/27/2017, 6:04 AM

Can you spot the mistake:

fun foo(key: Bar) = cache.getOrPut(key) { return somethingSomething(key) }

05/12/2017, 1:26 AM

ah well that's good to know that's there, but i'm looking for an equivalent of

isName

specifically which determines whether or not a string is a keyword in the language

voddan

05/22/2017, 6:22 PM

Looking for a workaround my first idea was a

Sequence

function like

File.readLinesInSequence(): Sequence<String>

. Is it possible to implement it?

05/27/2017, 3:38 AM

perhaps because it's declared

@InlineOnly

miha-x64

05/28/2017, 3:10 PM

infix fun Int.has(flag: Int) = this and flag == flag
infix fun Int.flagIf(condition: Boolean) = if (condition) this else 0

Haven't I reinvented a bicycle (or a wheel)? Or there's something similar in stdlib?

👍 1

ilya.gorbunov

05/31/2017, 6:55 PM

📣 For those who've tried Kotlin immutable collections and struggled with the operator importing we're going to suggest the following rather drastic solution: https://github.com/Kotlin/kotlinx.collections.immutable/issues/10#issuecomment-305277264 TLDR: We propose not to extend the immutable collections from read-only ones to mitigate this issue. If you have any objections or notes, please share them in that issue comments.

😱 1

🍻 1

👍 5

mg6maciej

06/02/2017, 10:09 AM

Was

Iterable<BigDecimal / BigInteger>.sum()

ever considered?

mg6maciej

06/02/2017, 10:11 AM

And more generally these kind of holes in #stdlib where we have

Iterable<Long>.sum()

, but not

List<*>.sumByLong

(like we have

sumBy

for ints and

sumByDouble

mg6maciej

06/02/2017, 11:25 AM

Double.doubleToLongBits

Double.longBitsToDouble

😕

😨 2

voddan

06/03/2017, 3:17 PM

Iterable

is not it since it returns a list

marcinmoskala

06/19/2017, 1:40 PM

true

marcinmoskala

06/19/2017, 3:10 PM

I prefer extensions over top-level functions because they are not suggested everywhere

ilya.gorbunov

06/22/2017, 12:39 PM

@natpryce Please submit your use cases to https://youtrack.jetbrains.com/issue/KT-17261, so we could know which part of its API should be exposed to multiplatform stdlib.

miha-x64

06/23/2017, 10:04 AM

Is there anything shorter than

Collections.unmodifiableList(someArray.toList())

pavlospt

06/26/2017, 9:30 AM

hello, so i was trying to find a more elegant way to write the following:

selectedChoices.mapIndexed { index, isSelected -> if (isSelected) index else -1 }.filter { it != -1 }

. Is there a prettier way to write this ? 🙂 In short what I want to do is get the indexes from

selectedChoices

, which is a BooleanArray, where the value is

true

and then map those indexes in something different, hence the

.filter { it != -1}

(also not sure if I am on the right channel)

gildor

06/30/2017, 2:02 AM

or more explicit and less cryptic:

listOf(2, 3, 4).flatMap { item ->
        if (item % 2 == 0) {
            List(2) { if (it == 0) item else -item }
        } else {
            listOf(item)
        }
    }

voddan

07/03/2017, 4:19 PM

Hm?

Pair

is not an optimization of

Triple

, they have different semantics. In addition, "pairwise" is unique in how obscure a naming it is

brk

07/07/2017, 8:09 AM

we already have nice

to<Type>OrNull()

string extensions https://github.com/Kotlin/KEEP/blob/master/proposals/stdlib/string-to-number.md But don't you think it would a good idea to add generalized version of 'try-or-null' to stdlib? like:

val date = tryOrNull { myAwesomeDateTimeParser.parse("2017-13-32") }

which is equal to:

val date = try { myAwesomeDateTimeParser.parse("2017-13-32") } catch(e: Exception) { null }

👍 1

pavlospt

08/08/2017, 7:44 AM

Does anyone know the reasoning behind this commit and the changes it introduced? https://github.com/JetBrains/kotlin/commit/5773594412660af11357ac9adc6ffcb45138b840

dmcg

08/10/2017, 2:05 PM

I wonder if we can summon @elizarov?

08/10/2017, 11:17 PM

can

@Throws

be renamed

@JvmThrows

and a

@Deprecated typealias

be added to map it back to

Throws

:youtrack: 1

👍 2

voddan

08/11/2017, 7:05 AM

What if Kotlin compiles to a platform which makes use of exception lists in function declarations? I think it is a pretty generic thing

dmcg

08/21/2017, 1:28 PM

@elizarov re Result type. It wasn't that it didn't open, just that I expected some sort of Algebraic data type, sealed class hierarchy.

karelpeeters

08/28/2017, 9:38 AM

What about

val items = ingredentsList.flatMap { listOf(ListItem.HeaderItem(it.type), ListItem.IngredientItem(it)) }

HeaderItem

will need a correctly implemented `equals`/`hascode` for this.

beholder

08/31/2017, 2:55 PM

Is it possible to compiler choose

AutoClosable.use()

instead of

Closable.use()

when class implements both interfaces? Implementation for AutoClosable is more simple and efficient.

ddsoyka

08/31/2017, 5:20 PM

is it safe to call

assertEquals(byteArray, otherByteArray)

and receive the expected result? Or do I need to call

Arrays.equals()

instead?

ddsoyka

08/31/2017, 5:38 PM

@jw Looks like someone already filed for it (https://github.com/kotlintest/kotlintest/issues/116)... maybe it's already in there?

elect

09/03/2017, 2:16 PM

https://github.com/kotlin-graphics/uno-sdk/blob/master/src/main/kotlin/uno/kotlin/buffers/intBuffer.kt

karelpeeters

09/08/2017, 9:20 AM

myMap.mapValuesTo(myMap) { ... }

might work, never tried it before.

dimsuz

09/08/2017, 9:20 AM

For now I did a simple:

inline fun <K, V> MutableMap<K,V>.replaceOrPut(key: K, updateOp: (V?) -> V): MutableMap<K, V> {
  val current = this[key]
  this[key] = updateOp(current)
  return this
}

Title

dimsuz

09/08/2017, 9:20 AM

For now I did a simple:

inline fun <K, V> MutableMap<K,V>.replaceOrPut(key: K, updateOp: (V?) -> V): MutableMap<K, V> {
  val current = this[key]
  this[key] = updateOp(current)
  return this
}

Nir

12/01/2020, 9:26 PM

Is there any chance of getting something like this in the standard library? Context:

inline fun <K, V> MutableMap<K,V>.replaceOrPut(key: K, updateOp: (V?) -> V): MutableMap<K, V> {
  val current = this[key]
  this[key] = updateOp(current)
  return this
}

I prefer to call this function update personally but the idea is the same. It's very useful. Without this I've found it's rather awkward to do certain things in Kotlin; updating for example integers in MutableMap<*, Int> is annoying, you can't even do

m["hello"] += 1

This is quite similar to Java hashmaps compute function: https://www.geeksforgeeks.org/hashmap-compute-method-in-java-with-examples/ which is absent in Kotlin's stdlib. Note that Python and C++ to take two examples, allow compound arithmetic on their mutable Maps, so this is fairly awkward relative to quite a number of existing mainstream languages

View count: 2