P04 - Find the number of elements of a list.

> length(listOf(1, 1, 2, 3, 5, 8))
6

kotlin

package org.kotlin99.lists

import com.natpryce.hamkrest.assertion.assertThat
import com.natpryce.hamkrest.equalTo
import org.junit.Test
import org.kotlin99.common.tail

fun <T> length(list: List<T>): Int =
    if (list.isEmpty()) 0 else 1 + length(list.tail())

class P04Test {
    @Test fun `find the number of elements of a list`() {
        assertThat(length(listOf<Int>()), equalTo(0))
        assertThat(length(listOf(1, 1, 2, 3, 5, 8)), equalTo(6))
    }
}