Advent of Code AoC 2020 - Programmering och digitalt

EDAA45 Programmering gk - Föreläsningar - Datavetenskap

The List is more like an array with dynamic length, List is one of the most used Collection type. [kotlin] val nextPage = 1 + pageIndexes.getOrElse(dataSource) { 0 } [/kotlin] Thanks to this, we save the condition that checks it. But another even more interesting thing is how we add a new item to the map. Maps in Kotlin have implemented + operator, so we can add a new item just doing map = map + Pair, which is the same as map += Pair. Kotlin vs Scala. GitHub Gist: instantly share code, notes, and snippets. A recent question on Kotlin’s Reddit came to my attention lately: 'Why is it bad to write extension functions for classes that you own?' One of the answer was that it was the opposite: it’s a good practice, and for several reasons.

It’s basically a way of saying “or else,” which you can see in this example: inline fun Map.getOrElse( key: K, defaultValue: -> V ): V. Returns the value for the given key, or the result of the defaultValue function if there was no entry for the given key. Kotlin comes with a wide range of extension methods to make collections manipulation easy. You can map, filter, find or whatever you want to do. No need to create utility methods, just use existing ones.

Introduktion till programmering med Scala - Datavetenskap

Returns a character at the given index or the result of calling the defaultValue function if the index is out of bounds of this char sequence. getOrElse. Returns the encapsulated value if this instance represents success or the result of onFailure function for the encapsulated Throwable exception if it is failure.

Är nullreferenser verkligen en dålig sak? 2021

GitHub Gist: instantly share code, notes, and snippets. A recent question on Kotlin’s Reddit came to my attention lately: 'Why is it bad to write extension functions for classes that you own?' One of the answer was that it was the opposite: it’s a good practice, and for several reasons. Among them were two very important ones that improve the design of one’s code: Able to call the function on a nullable. For a class with generic types, add a I am already experienced in Hibernate using Java and I have recently taken an interest in learning Kotlin.

fun main() { //sampleStart val numbers = listOf(1, 2, 3, 4) println(numbers.get(0)) println(numbers[0]) //numbers.get(5) // exception! kotlin-stdlib/kotlin.collections/getOrElse Platform and version requirements:JVM (1.0), JS (1.0), Native (1.0) Returns an element at the givenindexor the result of getOrElse provides safe access to elements of a collection. It takes an index and a function that provides the default value in cases when the index is out of bound.
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However, every time my function prints the map it ends with “kotlin.Unit”.

Some and None are declared as top level types. No need to write Optional.Some or Optional.None.
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Är nullreferenser verkligen en dålig sak? 2021

This guide walks through a basic setup and introduces chaining with maps. @kotlin.internal.InlineOnly public inline fun Map.getOrElse(key: K, defaultValue: -> V): V = get(key) ?: defaultValue() Which seems trivial at first glance, but is incorrect if V is nullable, which is allowed in Map. So if you use getOrElse on your map that can have null values, you're very likely making a mistake.

EDAA45 Programmering gk - Föreläsningar - Datavetenskap

Simply put, each type is non-nullable by default but can Kotlin runcatching fold. 4.

fun DoubleArray . getOrElse ( index : Int , defaultValue : ( Int ) -> Double ) : Double Inspired by Scalas Option getOrElse this method will return the non-null version of the nullable type unless it is null and thus returns the user defined result passed in. These are equivalent to the ?: operator except this provides a better syntax when chaining methods.