P09 - Pack consecutive duplicates of list elements into sublists.

> pack("aaaabccaadeeee".toList())
[[a, a, a, a], [b], [c, c], [a, a], [d], [e, e, e, e]]

kotlin

package org.kotlin99.lists

import com.natpryce.hamkrest.assertion.assertThat
import com.natpryce.hamkrest.equalTo
import org.junit.Test

fun <T> pack(list: List<T>): List<List<T>> =
    if (list.isEmpty()) emptyList()
    else {
        val packed = list.takeWhile { it == list.first() }
        listOf(packed) + pack(list.drop(packed.size))
    }

class P09Test {
    @Test fun `pack consecutive duplicates of list elements into sublists`() {
        assertThat(pack("a".toList()), equalTo(listOf("a".toList())))
        assertThat(pack("aaa".toList()), equalTo(listOf("aaa".toList())))
        assertThat(pack("aaaabccaadeeee".toList()), equalTo(listOf(
            "aaaa".toList(), "b".toList(), "cc".toList(), "aa".toList(), "d".toList(), "eeee".toList()
        )))
    }
}