`list fold mapOf a c gt a + c ` kotlinlang #getting-started

Channels

kotlin-foundation

compose-android

ohio-kotlin-users

kotlin-by-example

sofl-user-group

kotlin-multiplatform-contest

tricity-kotlin-user-group

kotlin-in-action

android-databinding

cincinnati-user-group

fluid-libraries

codemash-precompiler

kotlingforbeginners

jhipster-kotlin

prozis-android-backup

realworldkotlin

graviton-browser

spring-security

domain-driven-design

connect-audit-events

swiss-user-group

effectivekotlin

refactoring-to-kotlin

russian-kotlinasfirst

androidgithubprojects

introduce-yourself

pocketgitclient

effective-kotlin

algolialibraries

lambdaworld_cadiz

intellij-tricks

kotlin-pakistan

navigation-architecture-component

strife-discord-lib

machinelearningbawas

leedskotlinusergroup

stayhungrystayfoolish

kotest-contributors

practical-functional-programming

swagger-gradle-codegen

100daysofkotlin

kotlinultimatechallenge

pattern-matching

kotlinforbeginners

competitive-programming

compose-ui-showcase

competitivecoding

kotlin-data-storage

skia-wasm-interop-temp

java-to-kotlin-refactoring

event21-community-content

androidx-xprocessing

embedded-kotlin

fb-internal-demo

image-processing

myndocs-oauth2-server

kotlintest-devs

beepiz-libraries

kotlinprogrammers

cscenter-course-2016

k2-early-adopters

intellij-plugins

language-proposals

library-development

refreshversions

language-evolution

kotlinx-datetime

framework-elide

compose-desktop

jvm-ir-backend-feedback

android-architecture

100daysofkotlin-2021

github-workflows-kt

python-contributors

squarelibraries

arrow-contributors

codingconventions

getting-started

Title

k

karelpeeters

10/29/2018, 3:03 PM

list.fold(mapOf()) { a, c -> a + c }

h

henrik

10/29/2018, 3:05 PM

Thanks!

k

karelpeeters

10/29/2018, 3:06 PM

It's going to be quite inefficient if

list

is large, so be careful.

p

potter

10/29/2018, 3:09 PM

this would be more efficient, right?

list.fold(mutableMapOf<Int, Int>()) { a, b ->
	a.putAll(b)
	a
}

👍 1

k

karelpeeters

10/29/2018, 3:11 PM

Yeah, unfortunately it's ugly, arguably an abuse of

fold

and it returns something mutable.

mutableMapOf().apply { list.forEach { putAll(it) } as Map

would be another solution.

h

henrik

10/29/2018, 3:16 PM

kotlin should get collectEntries() from groovy 🙂

p

potter

10/29/2018, 3:16 PM

not necessarily more efficient, but definitely fun:

list.flatMap { it.entries.map { it.toPair() } }.toMap()

(not sure if there's a better way to get pairs from a list of maps)

j

Joris PZ

10/29/2018, 3:22 PM

How about

list.reduce { acc, map -> acc + map  }

Same caveats about large lists apply of course

👍 1

k

karelpeeters

10/29/2018, 6:44 PM

Doesn't work if

list

is empty!

✔️ 1

3 Views

#getting-started Join Slack