Migrate publishing to Sonatype s01 and Central Portal

- Updated build script to support publishing to Sonatype's s01.oss.sonatype.org, which is compatible with the new Maven Central Portal.
- Prioritized Central Portal credentials (CENTRAL_USERNAME, CENTRAL_PASSWORD) over legacy OSSRH credentials.
- Updated repository URLs for releases and snapshots to point to s01.oss.sonatype.org.
- Added documentation in README.md explaining the new publishing setup, environment variables, and Gradle tasks.

.github/dependabot.yml

@@ -0,0 +1,11 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
+
+version: 2
+updates:
+  - package-ecosystem: "" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "weekly"

.github/workflows/publishSnapshot.yml

@@ -2,7 +2,7 @@ name: Publish Snapshot
 
 on:
   push:
-    branches: [master, '14-**']
+    branches: [master]
 
 jobs:
   test:

.idea/AndroidProjectSystem.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="AndroidProjectSystem">
+    <option name="providerId" value="com.android.tools.idea.GradleProjectSystem" />
+  </component>
+</project>

.idea/gradle.xml

@@ -4,8 +4,9 @@
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
-        <option name="distributionType" value="WRAPPED" />
+        <option name="testRunner" value="CHOOSE_PER_TEST" />
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
+        <option name="gradleJvm" value="#GRADLE_LOCAL_JAVA_HOME" />
         <option name="modules">
           <set>
             <option value="$PROJECT_DIR$" />

.idea/kotlinScripting.xml

@@ -1,9 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="KotlinScriptingSettings">
-    <scriptDefinition className="org.jetbrains.kotlin.scripting.resolve.KotlinScriptDefinitionFromAnnotatedTemplate" definitionName="KotlinBuildScript">
-      <order>2147483647</order>
-      <autoReloadConfigurations>true</autoReloadConfigurations>
-    </scriptDefinition>
-  </component>
-</project>

.idea/misc.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_11" default="true" project-jdk-name="11" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="jbr-21" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>

.idea/runConfigurations.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="RunConfigurationProducerService">
+    <option name="ignoredProducers">
+      <set>
+        <option value="com.intellij.execution.junit.AbstractAllInDirectoryConfigurationProducer" />
+        <option value="com.intellij.execution.junit.AllInPackageConfigurationProducer" />
+        <option value="com.intellij.execution.junit.PatternConfigurationProducer" />
+        <option value="com.intellij.execution.junit.TestInClassConfigurationProducer" />
+        <option value="com.intellij.execution.junit.UniqueIdConfigurationProducer" />
+        <option value="com.intellij.execution.junit.testDiscovery.JUnitTestDiscoveryConfigurationProducer" />
+        <option value="org.jetbrains.kotlin.idea.junit.KotlinJUnitRunConfigurationProducer" />
+        <option value="org.jetbrains.kotlin.idea.junit.KotlinPatternConfigurationProducer" />
+      </set>
+    </option>
+  </component>
+</project>

.idea/vcs.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="VcsDirectoryMappings">
-    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+    <mapping directory="" vcs="Git" />
   </component>
 </project>

README.md

@@ -97,3 +97,24 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
+
+---
+
+## Publishing (Maven Central migration)
+
+This project is configured to publish via Sonatype's s01.oss.sonatype.org (Nexus) which is compatible with the new Central (central.sonatype.com). The old oss.sonatype.org host is no longer used.
+
+Environment variables supported by the build:
+- CENTRAL_USERNAME / CENTRAL_PASSWORD — Central Portal user/token (preferred)
+- OSSRH_USERNAME / OSSRH_PASSWORD — legacy credentials (fallback)
+- SIGNING_KEY_ID / SIGNING_KEY / SIGNING_PASSWORD — PGP signing (ASCII-armored key)
+- SNAPSHOT — set to true to append -SNAPSHOT to version
+
+Gradle tasks:
+- Publish all publications to Sonatype: `./gradlew publishAllPublicationsToSonatypeS01Repository`
+- Or, standard publish (selects snapshots vs releases by version): `./gradlew publish`
+
+Notes:
+- Releases are uploaded to: https://s01.oss.sonatype.org/service/local/staging/deploy/maven2/
+- Snapshots are uploaded to: https://s01.oss.sonatype.org/content/repositories/snapshots/
+- Staging/release close and promote are handled by Sonatype. If you use CI, set the env vars in your secrets.

build.gradle.kts

@@ -9,7 +9,7 @@ plugins {
 
 val PUBLISH_GROUP_ID = "com.github.adriankuta"
 val PUBLISH_ARTIFACT_ID = "tree-structure"
-val PUBLISH_VERSION = "3.0"
+val PUBLISH_VERSION = "3.1.0"
 
 val secretFile = File(rootProject.rootDir, "local.properties")
 if (secretFile.exists()) {
@@ -21,6 +21,10 @@ if (secretFile.exists()) {
         project.ext[name.toString()] = value
     }
 } else {
+    // Prefer Central Portal credentials via environment variables
+    project.ext["centralUsername"] = System.getenv("CENTRAL_USERNAME")
+    project.ext["centralPassword"] = System.getenv("CENTRAL_PASSWORD")
+    // Fallback legacy OSSRH credentials (still supported on s01)
     project.ext["ossrhUsername"] = System.getenv("OSSRH_USERNAME")
     project.ext["ossrhPassword"] = System.getenv("OSSRH_PASSWORD")
     project.ext["sonatypeStagingProfileId"] = System.getenv("SONATYPE_STAGING_PROFILE_ID")
@@ -74,15 +78,29 @@ publishing {
 
     repositories {
         maven {
-            name = "Sonatype"
-            val releasesRepoUrl = "https://oss.sonatype.org/service/local/staging/deploy/maven2"
-            val snapshotsRepoUrl = "https://oss.sonatype.org/content/repositories/snapshots"
+            name = "SonatypeS01"
+            // s01 is the supported Nexus host for Central publishing via Maven-compatible uploads
+            val releasesRepoUrl = "https://s01.oss.sonatype.org/service/local/staging/deploy/maven2/"
+            val snapshotsRepoUrl = "https://s01.oss.sonatype.org/content/repositories/snapshots/"
             url = uri(if (version.toString().endsWith("SNAPSHOT")) snapshotsRepoUrl else releasesRepoUrl)
             credentials {
+                // Prefer Central Portal credentials when provided, fallback to legacy OSSRH credentials
+                val centralUsername: String? by project
+                val centralPassword: String? by project
+                val CENTRAL_USERNAME: String? by project
+                val CENTRAL_PASSWORD: String? by project
                 val ossrhUsername: String? by project
                 val ossrhPassword: String? by project
-                username = ossrhUsername
-                password = ossrhPassword
+                username = centralUsername
+                    ?: CENTRAL_USERNAME
+                    ?: ossrhUsername
+                    ?: System.getenv("CENTRAL_USERNAME")
+                    ?: System.getenv("OSSRH_USERNAME")
+                password = centralPassword
+                    ?: CENTRAL_PASSWORD
+                    ?: ossrhPassword
+                    ?: System.getenv("CENTRAL_PASSWORD")
+                    ?: System.getenv("OSSRH_PASSWORD")
             }
         }
     }
@@ -118,6 +136,12 @@ kotlin {
             }
         }
     }
+
+    // Add iOS targets
+    iosX64()
+    iosArm64()
+    iosSimulatorArm64()
+
     val hostOs = System.getProperty("os.name")
     val isMingwX64 = hostOs.startsWith("Windows")
     val nativeTarget = when {
@@ -127,7 +151,6 @@ kotlin {
         else -> throw GradleException("Host OS is not supported in Kotlin/Native.")
     }
 
-
     sourceSets {
         val commonMain by getting
         val commonTest by getting {
@@ -135,11 +158,29 @@ kotlin {
                 implementation(kotlin("test"))
             }
         }
-        val jvmMain by getting
+        val jvmMain by getting {
+            dependencies {
+                implementation(kotlin("script-runtime"))
+            }
+        }
         val jvmTest by getting
         val jsMain by getting
         val jsTest by getting
         val nativeMain by getting
         val nativeTest by getting
+
+        // Shared iOS source sets
+        val iosMain by creating {
+            dependsOn(commonMain)
+        }
+        val iosTest by creating {
+            dependsOn(commonTest)
+        }
+        val iosX64Main by getting { dependsOn(iosMain) }
+        val iosArm64Main by getting { dependsOn(iosMain) }
+        val iosSimulatorArm64Main by getting { dependsOn(iosMain) }
+        val iosX64Test by getting { dependsOn(iosTest) }
+        val iosArm64Test by getting { dependsOn(iosTest) }
+        val iosSimulatorArm64Test by getting { dependsOn(iosTest) }
     }
 }

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.2-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

gradlew

@@ -55,7 +55,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.
@@ -80,13 +80,11 @@ do
     esac
 done
 
-APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
-
-APP_NAME="Gradle"
+# This is normally unused
+# shellcheck disable=SC2034
 APP_BASE_NAME=${0##*/}
-
-# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD=maximum
@@ -133,22 +131,29 @@ location of your Java installation."
     fi
 else
     JAVACMD=java
-    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
+    fi
 fi
 
 # Increase the maximum file descriptors if we can.
 if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
     case $MAX_FD in #(
       max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
         MAX_FD=$( ulimit -H -n ) ||
             warn "Could not query maximum file descriptor limit"
     esac
     case $MAX_FD in  #(
       '' | soft) :;; #(
       *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
         ulimit -n "$MAX_FD" ||
             warn "Could not set maximum file descriptor limit to $MAX_FD"
     esac
@@ -193,11 +198,15 @@ if "$cygwin" || "$msys" ; then
     done
 fi
 
-# Collect all arguments for the java command;
-#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
-#     shell script including quotes and variable substitutions, so put them in
-#     double quotes to make sure that they get re-expanded; and
-#   * put everything else in single quotes, so that it's not re-expanded.
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
@@ -205,6 +214,12 @@ set -- \
         org.gradle.wrapper.GradleWrapperMain \
         "$@"
 
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
 # Use "xargs" to parse quoted args.
 #
 # With -n1 it outputs one arg per line, with the quotes and backslashes removed.

gradlew.bat

@@ -14,7 +14,7 @@
 @rem limitations under the License.
 @rem
 
-@if "%DEBUG%" == "" @echo off
+@if "%DEBUG%"=="" @echo off
 @rem ##########################################################################
 @rem
 @rem  Gradle startup script for Windows
@@ -25,7 +25,8 @@
 if "%OS%"=="Windows_NT" setlocal
 
 set DIRNAME=%~dp0
-if "%DIRNAME%" == "" set DIRNAME=.
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
@@ -40,7 +41,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto execute
+if %ERRORLEVEL% equ 0 goto execute
 
 echo.
 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
@@ -75,13 +76,15 @@ set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
 :end
 @rem End local scope for the variables with windows NT shell
-if "%ERRORLEVEL%"=="0" goto mainEnd
+if %ERRORLEVEL% equ 0 goto mainEnd
 
 :fail
 rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
 rem the _cmd.exe /c_ return code!
-if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
-exit /b 1
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
 
 :mainEnd
 if "%OS%"=="Windows_NT" endlocal

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNode.kt

@@ -1,11 +1,20 @@
 package com.github.adriankuta.datastructure.tree
 
-import com.github.adriankuta.datastructure.tree.TreeNodeIterators.*
+import com.github.adriankuta.datastructure.tree.exceptions.TreeNodeException
+import com.github.adriankuta.datastructure.tree.iterators.LevelOrderTreeIterator
+import com.github.adriankuta.datastructure.tree.iterators.PostOrderTreeIterator
+import com.github.adriankuta.datastructure.tree.iterators.PreOrderTreeIterator
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators.*
 import kotlin.jvm.JvmSynthetic
 
-open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationInterface<T> {
+/**
+ * @param treeIterator Choose one of available iterators from [TreeNodeIterators]
+ */
+open class TreeNode<T>(val value: T, var treeIterator: TreeNodeIterators = PreOrder) : Iterable<TreeNode<T>>, ChildDeclarationInterface<T> {
 
     private var _parent: TreeNode<T>? = null
+
     /**
      * The converse notion of a child, an immediate ancestor.
      */
@@ -13,6 +22,7 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
         get() = _parent
 
     private val _children = mutableListOf<TreeNode<T>>()
+
     /**
      * A group of nodes with the same parent.
      */
@@ -20,9 +30,11 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
         get() = _children
 
     /**
-     * Choose one of available iterators from [TreeNodeIterators]
+     * Checks whether the current tree node is the root of the tree
+     * @return `true` if the current tree node is root of the tree, `false` otherwise.
      */
-    var defaultIterator: TreeNodeIterators = PreOrder
+    val isRoot: Boolean
+        get() = _parent == null
 
     /**
      * Add new child to current node or root.
@@ -37,7 +49,8 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
     @JvmSynthetic
     override fun child(value: T, childDeclaration: ChildDeclaration<T>?): TreeNode<T> {
         val newChild = TreeNode(value)
-        if(childDeclaration != null)
+        newChild._parent = this
+        if (childDeclaration != null)
             newChild.childDeclaration()
         _children.add(newChild)
         return newChild
@@ -91,6 +104,31 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
         return depth
     }
 
+    /**
+     * Returns the collection of nodes, which connect the current node
+     * with its descendants
+     *
+     * @param descendant the bottom child node for which the path is calculated
+     * @return collection of nodes, which connect the current node with its descendants
+     * @throws TreeNodeException exception that may be thrown in case if the
+     *                           current node does not have such descendant or if the
+     *                           specified tree node is root
+     */
+    @Throws(TreeNodeException::class)
+    fun path(descendant: TreeNode<T>): List<TreeNode<T>> {
+
+        val path = mutableListOf<TreeNode<T>>()
+        var node = descendant
+        path.add(node)
+        while (!node.isRoot) {
+            node = node.parent!!
+            path.add(node)
+            if (node == this)
+                return path
+        }
+        throw TreeNodeException("The specified tree node $descendant is not the descendant of tree node $this")
+    }
+
     /**
      * Remove all children from root and every node in tree.
      */
@@ -126,9 +164,9 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
     }
 
     /**
-     * You can change default iterator by changing [defaultIterator] property.
+     * You can change default iterator by changing [treeIterator] property.
      */
-    override fun iterator(): Iterator<TreeNode<T>> = when (defaultIterator) {
+    override fun iterator(): Iterator<TreeNode<T>> = when (treeIterator) {
         PreOrder -> PreOrderTreeIterator(this)
         PostOrder -> PostOrderTreeIterator(this)
         LevelOrder -> LevelOrderTreeIterator(this)

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNodeExt.kt

@@ -1,5 +1,6 @@
 package com.github.adriankuta.datastructure.tree
 
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
 import kotlin.jvm.JvmSynthetic
 
 typealias ChildDeclaration<T> = ChildDeclarationInterface<T>.() -> Unit
@@ -18,8 +19,7 @@ inline fun <reified T> tree(
     defaultIterator: TreeNodeIterators = TreeNodeIterators.PreOrder,
     childDeclaration: ChildDeclaration<T>
 ): TreeNode<T> {
-    val treeNode = TreeNode(root)
-    treeNode.defaultIterator = defaultIterator
+    val treeNode = TreeNode(root, defaultIterator)
     treeNode.childDeclaration()
     return treeNode
 }

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/exceptions/TreeNodeException.kt

@@ -0,0 +1,6 @@
+package com.github.adriankuta.datastructure.tree.exceptions
+
+import kotlin.jvm.JvmOverloads
+
+class TreeNodeException @JvmOverloads constructor(message: String? = null, cause: Throwable? = null) :
+    RuntimeException(message, cause)

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/iterators/LevelOrderTreeIterator.kt

@@ -1,4 +1,6 @@
-package com.github.adriankuta.datastructure.tree
+package com.github.adriankuta.datastructure.tree.iterators
+
+import com.github.adriankuta.datastructure.tree.TreeNode
 
 /**
  * Tree is iterated by using `Level-order Traversal Algorithm"

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/iterators/PostOrderTreeIterator.kt

@@ -1,4 +1,6 @@
-package com.github.adriankuta.datastructure.tree
+package com.github.adriankuta.datastructure.tree.iterators
+
+import com.github.adriankuta.datastructure.tree.TreeNode
 
 /**
  * Tree is iterated by using `Post-order Traversal Algorithm"

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/iterators/PreOrderTreeIterator.kt

@@ -1,4 +1,6 @@
-package com.github.adriankuta.datastructure.tree
+package com.github.adriankuta.datastructure.tree.iterators
+
+import com.github.adriankuta.datastructure.tree.TreeNode
 
 /**
  * Tree is iterated by using `Pre-order Traversal Algorithm"

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/iterators/TreeNodeIterators.kt

@@ -1,4 +1,4 @@
-package com.github.adriankuta.datastructure.tree
+package com.github.adriankuta.datastructure.tree.iterators
 
 /**
  * @see PreOrder

src/commonTest/kotlin/com.github.adriankuta/datastructure.tree/TreeNodeTest.kt

@@ -1,5 +1,6 @@
 package com.github.adriankuta.datastructure.tree
 
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
 import kotlin.test.Test
 import kotlin.test.assertContentEquals
 import kotlin.test.assertEquals

src/jvmMain/kotlin/Example.ws.kts

@@ -0,0 +1,14 @@
+import com.github.adriankuta.datastructure.tree.tree
+
+val root =
+    tree("World") {
+        child("North America") {
+            child("USA")
+        }
+        child("Europe") {
+            child("Poland")
+            child("Germany")
+        }
+    }
+
+print(root.prettyString())