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The Kotlin Programming Language.

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The Swift Programming Language

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The Go programming language

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Simple, fast, safe, compiled language for developing maintainable software. Compiles itself in <1s with zero library dependencies. Supports automatic C => V translation. https://vlang.io

Quick Overview

Kotlin is a modern, cross-platform, statically typed programming language developed by JetBrains. It is fully interoperable with Java and Android, offering a more concise and expressive syntax while maintaining full compatibility with existing Java code.

Pros

  • Concise and expressive syntax, reducing boilerplate code
  • Full interoperability with Java, allowing gradual adoption in existing projects
  • Null safety features, helping to prevent null pointer exceptions
  • Coroutines support for efficient asynchronous programming

Cons

  • Slower compilation times compared to Java, especially for large projects
  • Smaller community and ecosystem compared to more established languages
  • Learning curve for developers coming from Java or other languages
  • Some advanced features may lead to increased code complexity if not used judiciously

Code Examples

  1. Null safety example:
fun printLength(str: String?) {
    println(str?.length ?: "String is null")
}

This code demonstrates Kotlin's null safety features, using the safe call operator ?. and the elvis operator ?:.

  1. Data class example:
data class Person(val name: String, val age: Int)

val person = Person("Alice", 30)
println(person) // Output: Person(name=Alice, age=30)

This example shows how to create a data class in Kotlin, which automatically provides useful methods like toString(), equals(), and hashCode().

  1. Coroutines example:
import kotlinx.coroutines.*

suspend fun fetchData(): String {
    delay(1000) // Simulate network delay
    return "Data fetched"
}

fun main() = runBlocking {
    val result = async { fetchData() }
    println("Doing other work...")
    println(result.await())
}

This code demonstrates the use of Kotlin coroutines for asynchronous programming, allowing for efficient concurrent execution.

Getting Started

To start using Kotlin in your project:

  1. Install the Kotlin plugin in your IDE (e.g., IntelliJ IDEA or Android Studio).
  2. Create a new Kotlin file with a .kt extension.
  3. Write your Kotlin code, for example:
fun main() {
    println("Hello, Kotlin!")
}
  1. Compile and run your Kotlin code using the IDE or command-line tools.

For more detailed instructions and documentation, visit the official Kotlin website: https://kotlinlang.org/docs/getting-started.html

Competitor Comparisons

100,112

TypeScript is a superset of JavaScript that compiles to clean JavaScript output.

Pros of TypeScript

  • Larger ecosystem and community support
  • Better integration with JavaScript and existing web technologies
  • More extensive tooling and IDE support across various platforms

Cons of TypeScript

  • Steeper learning curve for developers new to static typing
  • Compilation step required, which can slow down development workflow
  • Type definitions for third-party libraries may be incomplete or outdated

Code Comparison

TypeScript:

interface Person {
  name: string;
  age: number;
}

function greet(person: Person): string {
  return `Hello, ${person.name}! You are ${person.age} years old.`;
}

Kotlin:

data class Person(val name: String, val age: Int)

fun greet(person: Person): String {
    return "Hello, ${person.name}! You are ${person.age} years old."
}

Both TypeScript and Kotlin offer strong typing and object-oriented features. TypeScript's syntax is more familiar to JavaScript developers, while Kotlin's concise syntax and null safety features appeal to many developers. TypeScript excels in web development scenarios, whereas Kotlin is more versatile, supporting both frontend and backend development across various platforms.

67,285

The Swift Programming Language

Pros of Swift

  • Faster compilation times for large projects
  • More mature support for iOS and macOS development
  • Stronger emphasis on protocol-oriented programming

Cons of Swift

  • Less cross-platform support compared to Kotlin
  • Steeper learning curve for developers new to Apple ecosystems
  • Smaller community and ecosystem outside of Apple platforms

Code Comparison

Swift:

let numbers = [1, 2, 3, 4, 5]
let doubled = numbers.map { $0 * 2 }
print(doubled)

Kotlin:

val numbers = listOf(1, 2, 3, 4, 5)
val doubled = numbers.map { it * 2 }
println(doubled)

Both languages offer concise syntax for functional programming concepts like mapping. Swift uses $0 as a shorthand for the first parameter in closures, while Kotlin uses it. The overall structure and readability are similar, showcasing the modern, expressive nature of both languages.

Swift excels in Apple ecosystem development, offering seamless integration with iOS and macOS. Kotlin, on the other hand, provides better cross-platform support and is more widely adopted for Android development. While Swift has a steeper learning curve for those unfamiliar with Apple's ecosystem, Kotlin's similarity to Java makes it more accessible to a broader range of developers.

10,195

The Dart SDK, including the VM, JS and Wasm compilers, analysis, core libraries, and more.

Pros of sdk

  • Designed specifically for web and mobile development, with strong support for Flutter
  • Faster compilation times and hot reload feature for quicker development cycles
  • Simpler syntax and easier learning curve for developers new to the language

Cons of sdk

  • Less mature ecosystem compared to Kotlin, with fewer libraries and tools available
  • Limited use outside of web and mobile development, whereas Kotlin is more versatile
  • Smaller community and fewer resources for learning and problem-solving

Code Comparison

Dart (sdk):

void main() {
  var list = [1, 2, 3];
  list.forEach((item) => print(item));
}

Kotlin:

fun main() {
    val list = listOf(1, 2, 3)
    list.forEach { println(it) }
}

Both examples demonstrate similar functionality, but Dart's syntax is slightly more verbose with the use of parentheses and arrow functions. Kotlin's syntax is more concise, using curly braces and implicit it parameter.

While both languages have their strengths, Kotlin offers broader applicability across different platforms and a more extensive ecosystem. Dart, on the other hand, excels in web and mobile development, particularly when used with Flutter. The choice between the two depends on the specific project requirements and target platforms.

123,517

The Go programming language

Pros of Go

  • Simpler language design with fewer features, leading to faster compilation and easier onboarding
  • Built-in concurrency support with goroutines and channels
  • Stronger focus on systems programming and network applications

Cons of Go

  • Less expressive syntax compared to Kotlin's more modern language features
  • Lack of generics (until Go 1.18) and functional programming constructs
  • Limited support for null safety compared to Kotlin's robust null handling

Code Comparison

Go:

func main() {
    ch := make(chan int)
    go func() { ch <- 42 }()
    fmt.Println(<-ch)
}

Kotlin:

fun main() {
    runBlocking {
        val channel = Channel<Int>()
        launch { channel.send(42) }
        println(channel.receive())
    }
}

This comparison demonstrates the difference in concurrency handling between Go and Kotlin. Go uses goroutines and channels, while Kotlin employs coroutines and channels from the kotlinx.coroutines library. Both achieve similar results, but Go's approach is more built-in and straightforward, while Kotlin's is more flexible and integrated with other language features.

96,644

Empowering everyone to build reliable and efficient software.

Pros of Rust

  • Memory safety without garbage collection, offering better performance and control
  • Powerful concurrency model with zero-cost abstractions
  • Extensive ecosystem with cargo package manager and crates.io

Cons of Rust

  • Steeper learning curve due to complex concepts like ownership and lifetimes
  • Longer compilation times compared to Kotlin
  • Less mature tooling and IDE support than Kotlin's JetBrains ecosystem

Code Comparison

Rust:

fn main() {
    let numbers = vec![1, 2, 3, 4, 5];
    let sum: i32 = numbers.iter().sum();
    println!("Sum: {}", sum);
}

Kotlin:

fun main() {
    val numbers = listOf(1, 2, 3, 4, 5)
    val sum = numbers.sum()
    println("Sum: $sum")
}

Both Rust and Kotlin are modern programming languages with strong type systems and expressive syntax. Rust focuses on systems programming and memory safety, while Kotlin targets multiplatform development with a focus on Java interoperability. Rust's performance and safety features make it ideal for low-level systems, while Kotlin's ease of use and JVM integration make it popular for Android and server-side development.

35,757

Simple, fast, safe, compiled language for developing maintainable software. Compiles itself in <1s with zero library dependencies. Supports automatic C => V translation. https://vlang.io

Pros of V

  • Faster compilation times and smaller binary sizes
  • C-like syntax that may be more familiar to some developers
  • Built-in memory management without garbage collection

Cons of V

  • Less mature ecosystem and community compared to Kotlin
  • Fewer libraries and third-party tools available
  • Still in active development, with potential for breaking changes

Code Comparison

V:

fn main() {
    println('Hello, World!')
}

Kotlin:

fun main() {
    println("Hello, World!")
}

Summary

V is a newer language focusing on simplicity and performance, while Kotlin is a more established language with extensive tooling and ecosystem support. V offers faster compilation and smaller binaries, but Kotlin provides a more mature development environment and wider adoption in various domains, especially Android development.

Both languages aim to improve upon existing languages (C and Java, respectively) while maintaining familiarity. V's syntax is closer to C, while Kotlin builds on Java's ecosystem. The choice between them depends on specific project requirements, existing infrastructure, and developer preferences.

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README

official project TeamCity (simple build status) Maven Central GitHub license Revved up by Develocity

Kotlin Programming Language

Welcome to Kotlin!
It is an open-source, statically typed programming language supported and developed by JetBrains and open-source contributors.

Some handy links:

Kotlin Multiplatform capabilities

Support for multiplatform programming is one of Kotlin’s key benefits. It reduces time spent writing and maintaining the same code for different platforms while retaining the flexibility and benefits of native programming.

Editing Kotlin

Build environment requirements

This repository is using Gradle toolchains feature to select and auto-provision required JDKs from AdoptOpenJdk project.

Alternatively, it is still possible to only provide required JDKs via environment variables (see gradle.properties for supported variable names). To ensure Gradle uses only JDKs from environmental variables - disable Gradle toolchain auto-detection by passing -Porg.gradle.java.installations.auto-detect=false option (or put it into $GRADLE_USER_HOME/gradle.properties).

On Windows you might need to add long paths setting to the repo:

git config core.longpaths true 

Building

The project is built with Gradle. Run Gradle to build the project and to run the tests using the following command on Unix/macOS:

./gradlew <tasks-and-options>

or the following command on Windows:

gradlew <tasks-and-options>

On the first project configuration gradle will download and setup the dependencies on

  • intellij-core is a part of command line compiler and contains only necessary APIs.
  • idea-full is a full blown IntelliJ IDEA Community Edition to be used in the plugin module.

These dependencies are quite large, so depending on the quality of your internet connection you might face timeouts getting them. In this case, you can increase timeout by specifying the following command line parameters on the first run:

./gradlew -Dhttp.socketTimeout=60000 -Dhttp.connectionTimeout=60000

Important gradle tasks

  • clean - clean build results
  • dist - assembles the compiler distribution into dist/kotlinc/ folder
  • install - build and install all public artifacts into local maven repository
  • coreLibsTest - build and run stdlib, reflect and kotlin-test tests
  • gradlePluginTest - build and run gradle plugin tests
  • compilerTest - build and run all compiler tests

To reproduce TeamCity build use -Pteamcity=true flag. Local builds don't run proguard and have jar compression disabled by default.

OPTIONAL: Some artifacts, mainly Maven plugin ones, are built separately with Maven. Refer to libraries/ReadMe.md for details.

To build Kotlin/Native, see kotlin-native/README.md.

Working with the project in IntelliJ IDEA

It is recommended to use the latest released version of Intellij IDEA (Community or Ultimate Edition). You can download IntelliJ IDEA here.

After cloning the project, import the project in IntelliJ by choosing the project directory in the Open project dialog.

For handy work with compiler tests it's recommended to use Kotlin Compiler Test Helper

Dependency verification

We have a dependencies verification feature enabled in the repository for all Gradle builds. Gradle will check hashes (md5 and sha256) of used dependencies and will fail builds with Dependency verification failed errors when local artifacts are absent or have different hashes listed in the verification-metadata.xml file.

It's expected that verification-metadata.xml should only be updated with the commits that modify the build. There are some tips how to perform such updates:

  • Delete components section of verification-metadata.xml to avoid stockpiling of old unused dependencies. You may use the following command:
#macOS
sed -i '' -e '/<components>/,/<\/components>/d' gradle/verification-metadata.xml
#Linux & Git for Windows
sed -i -e '/<components>/,/<\/components>/d' gradle/verification-metadata.xml
  • Re-generate dependencies with Gradle's --write-verification-metadata command (verify update relates to your changes)
./gradlew --write-verification-metadata sha256,md5 -Pkotlin.native.enabled=true resolveDependencies

resolveDependencies task resolves dependencies for all platforms including dependencies downloaded by plugins.

Keep in mind:

  • If you’re adding a dependency with OS mentioned in an artifact name (darwin, mac, osx, linux, windows), remember to add them to implicitDependencies configuration or update resolveDependencies task if needed. resolveDependencies should resolve all dependencies including dependencies for different platforms.
  • If you have a local.properties file in your Kotlin project folder, make sure that it doesn't contain kotlin.native.enabled=false. Otherwise, native-only dependencies may not be added to the verification metadata. This is because local.properties has higher precedence than the -Pkotlin.native.enabled=true specified in the Gradle command.

Using -dev versions

We publish -dev versions frequently.

For -dev versions you can use the list of available versions and include this maven repository:

maven("https://maven.pkg.jetbrains.space/kotlin/p/kotlin/bootstrap")

License

Kotlin is distributed under the terms of the Apache License (Version 2.0). See license folder for details.

Contributing

Please be sure to review Kotlin's contributing guidelines to learn how to help the project.