public inline fun Iterable.fold(initial: R, operation: (acc: R, T) -> R): R ) This function helps to accumulate value starting with initial value, then apply operation from left to right to current accumulator value and each element. – Kotlin sum(), sumBy(), sumByDouble() and BigDecimal in List, Map example – Kotlin List & Mutable List tutorial with examples The source code of custom Range you can find here.In this tutorial, I will show you some examples that use Kotlin fold and fold indexed methods to accumulate List and Map. We can also use the in operator as part of for-loops: for (i in 'a'.'f') ') char var1 = 'a' ĬharRange characters = new CharRange(var1, 'z') īoolean isPresent = ntains('f') However, under the hood, the contains function from CharRange will be used. Val isPresent = 'f' in 'a'.rangeTo('c') // FALSE Val isPresent = 'f' in characters // TRUE Let's start with checking that a character f is a part of a specific Range.

We can use the in operator with Range objects to know if a value is presented in a specific Range. Val numbersWithStep = 1.5 step 2 // 1 3 5 The IntProgression, CharProgression and LongProgression supports the custom step for progressions. characters is an objects of CharProgression type.numbers is an object of IntProgression type.Val characters = 'c'.downTo('a') // c b aīoth of these samples create Progressions, and we can use a different form of creating ranges. In this case, the Progression object will be created. Suppose we want to create a sequence of numbers from the largest number number to the smallest one. In Kotlin defined specific types for arithmetic progressions of Char, Int and Long. Ranges are defined for comparable types: having an order, you can define whether an arbitrary instance is in the range between two given instances. characters is an objects of CharRange typeĪ range defines a closed interval in the mathematical sense: it is defined by its two endpoint values, which are both included in the range.Val characters = 'a'.rangeTo('z') // all letters from 'a' to 'z'īoth of these samples create Ranges, and we can use a different form of creating ranges. We can create a Range of integers and Range of chars: val numbers = 1.5 // 1 2 3 4 5 In the end, we create a custom range for the delivery time of a restaurant base on open and close time. Let's explore Ranges in Kotlin and understand how it can simplify development.

Kotlin range to list