I'm a complete noob to Kotlin so I may be missing the point but the project doesn't build and currently errors in workshop-jb/src/ii_conventions/_15_OperatorsOverloading.kt

Hi Friends!

I dare to suggest this pom.xml which uses kotlin-maven-plugin to allow building the exercises and testing them with maven (as another option in addition to having idea / eclipse project files).

Just cloned and I get the following:

 ./gradlew test

FAILURE: Build failed with an exception.

* Where:
Build file '/workspace/kotlin-koans/build.gradle' line: 15

* What went wrong:
A problem occurred evaluating root project 'kotlin-koans'.
> Failed to apply plugin [id 'kotlin2js']
   > Cannot add extension with name 'kotlin', as there is an extension already registered with that name.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Total time: 0.762 secs

Error:(6, 31) Kotlin: Accidental override: The following declarations have the same JVM signature (getMessage()Ljava/lang/String;):
    fun <get-message>(): kotlin.String
    fun getMessage(): kotlin.String?

Figure there's a change you guys might want to investigate. I get 237 errors and failure at compilation, all along the lines of

Error:(5, 1) Kotlin: 'public fun todoTask0(): kotlin.Nothing' is already defined in i_introduction._0_Hello_World.Hello

Error:(7, 5) Kotlin: Redeclaration: idea

This is happening with plugin version 1.0.0-beta-2429-IJ143-19

Full output here: https://gist.github.com/hzsweers/7e341269f824c05232e8

Was there a language change regarding using Ranges in a forEach loop? (I'm on kotlin 1.0 beta)

In iii_conventions/_RangeTo.kt :

for (date in firstDate..secondDate) {
       handler(date)
}

Will not compile for me. I am pretty sure I have my DateRange implemented correctly.

Thank you! Loving Kotlin!

Just opening the project with the latest inteliJ community edition and hitting All Tests gives me 26 errors. Here is a screenshot of the first one. I have installed the kotlin plugin and ran my own 'hello world' project without issues.

Caution - I'm a newbie.

for n31, my solution looks the same as the 'resolution' version, but doesn't pass the test I think because of the declarations of

operator fun Invokable.invoke(): Nothing = todoTask31()
fun Invokable.getNumberOfInvocations(): Nothing = todoTask31()

in the test class.

Note that the resolution doesn't pass either, I believe for the same reason? Can you give me a hint? My solution is

class Invokable (private var count : Int = 0) {

 operator fun invoke() : Invokable {
     count++
     return this
 }

 fun getNumberOfInvocations() : Int = count

}

Apologies if I'm being an idiot.

I think the logic for calculating dates from millis and vice versa was incorrect. Java.util.Calendar uses zero based months to keep you on your toes! Also Calendar.getInstance() will get the default Locale (and also timezone) so the toMillis conversions it produces will be adjusted accordingly.

For example, Dates in December don't work with the old code! e.g. MyDate(2014, 12, 13) would create a date of: "2015-01-13" (Jan 13th 2015).

The orignal asserts in the tests were removed here: https://github.com/Kotlin/kotlin-koans/commit/fdc9d249005cf68fd2f9326356aef534edbc648d, because they were not reliable because of the above reasons, but I think their original intentions remain valid, so I have reinstated them and amended the calendar logic to be compatible with zero-based months and always use UTC.

The time in millis in the previous tests had an offset included, so when converted to UTC: 1392220800000 = 2014-02-12T16:00

So I have changed it to: 1389571200000 = 2014-01-13T00:00

This should yield succesfull test results when ran in different locales.

Hi,

nowadays content of MyDate.kt is more objected-like and it does not look fancy (as it could):

data class MyDate(val year: Int, val month: Int, val dayOfMonth: Int) : Comparable<MyDate>{
    override fun compareTo(other: MyDate): Int{
        if(year != other.year) return year - other.year
        if(month != other.month) return month - other.month
        return dayOfMonth - other.dayOfMonth
    }
}

operator fun MyDate.rangeTo(other: MyDate) = DateRange(this, other)

I think that better purpose for this Kotlin programming language course would be rewrite existing code using a functional programming paradign. Here's my solution:

data class MyDate(val year: Int, val month: Int, val dayOfMonth: Int) : Comparable<MyDate>{
    override fun compareTo(other: MyDate): Int = when {
        year != other.year -> year - other.year
        month != other.month -> month - other.month
        else -> dayOfMonth - other.dayOfMonth
    }
}

operator fun MyDate.rangeTo(other: MyDate) = DateRange(this, other)

I must agree that change is pretty small, but as you provide in kotlin-koans course typical functional structures like lambdas or recursion, maybe it would be better to keep this course and its code functional, than messing it with 'java-like' code.

Although, I found fun in rewriting every MyDate.kt instance and that was good additional trainign :-D

Hope you would find useful. Cheers!

Hey folks,

Just getting into Kotlin and I had a hard time importing the koans into Intellij. Can we make it a Maven project and/or remove the editor settings (e.g., Eclipse files like .project)?

Environment：MacOS、Gradle 4.9 IDE：IntelliJ IDEA CE 2019.03 JDK : 1.8.0_111

1. After join the course，always alert ”Kotlin Koans：failed“，don't have other info for this error 2.Click ”check“ in the task description，alert ”No tests have run“

Related to #173.

• build.gradle file has been removed.
• build.gradle.kts file has been added with content equivalent to the former build.gradle file.
• ~Gradle wrapper has been upgraded to the current Gradle version 5.2.1 because of better and more stable support of Kotlin DSL.~

I'm just wondering - if the project is build by Gradle, why not to build it via Gradle Kotlin DSL? Wouldn't it be more appropriate?

I've already did it in my fork of the project (see build.gradle.kts), so I can prepare a pull request.