Svetlana Isakova
81 lines
3.0 KiB
Kotlin
81 lines
3.0 KiB
Kotlin
package iterators
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import kotlin.test.assertEquals
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import org.junit.Test as test
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import kotlin.test.failsWith
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fun fibonacci(): Iterator<Int> {
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// fibonacci terms
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var index = 0; var a = 0; var b = 1
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return iterate<Int> { when (index++) { 0 -> a; 1 -> b; else -> { val result = a + b; a = b; b = result; result } } }
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}
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class IteratorsTest {
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test fun filterAndTakeWhileExtractTheElementsWithinRange() {
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assertEquals(arrayList(144, 233, 377, 610, 987), fibonacci().filter { it > 100 }.takeWhile { it < 1000 }.toList())
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}
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test fun foldReducesTheFirstNElements() {
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val sum = { (a: Int, b: Int) -> a + b }
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assertEquals(arrayList(13, 21, 34, 55, 89).fold(0, sum), fibonacci().filter { it > 10 }.take(5).fold(0, sum))
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}
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test fun takeExtractsTheFirstNElements() {
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assertEquals(arrayList(0, 1, 1, 2, 3, 5, 8, 13, 21, 34), fibonacci().take(10).toList())
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}
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test fun mapAndTakeWhileExtractTheTransformedElements() {
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assertEquals(arrayList(0, 3, 3, 6, 9, 15), fibonacci().map { it * 3 }.takeWhile { (i: Int) -> i < 20 }.toList())
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}
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test fun joinConcatenatesTheFirstNElementsAboveAThreshold() {
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assertEquals("13, 21, 34, 55, 89, ...", fibonacci().filter { it > 10 }.makeString(separator = ", ", limit = 5))
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}
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test fun plus() {
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val iter = arrayList("foo", "bar").iterator()
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val iter2 = iter + "cheese"
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assertEquals(arrayList("foo", "bar", "cheese"), iter2.toList())
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// lets use a mutable variable
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var mi = arrayList("a", "b").iterator()
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mi += "c"
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assertEquals(arrayList("a", "b", "c"), mi.toList())
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}
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test fun plusCollection() {
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val a = arrayList("foo", "bar")
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val b = arrayList("cheese", "wine")
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val iter = a.iterator() + b.iterator()
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assertEquals(arrayList("foo", "bar", "cheese", "wine"), iter.toList())
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// lets use a mutable variable
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var ml = arrayList("a").iterator()
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ml += a.iterator()
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ml += "beer"
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ml += b
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ml += "z"
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assertEquals(arrayList("a", "foo", "bar", "beer", "cheese", "wine", "z"), ml.toList())
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}
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test fun requireNoNulls() {
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val iter = arrayList<String?>("foo", "bar").iterator()
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val notNull = iter.requireNoNulls()
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assertEquals(arrayList("foo", "bar"), notNull.toList())
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val iterWithNulls = arrayList("foo", null, "bar").iterator()
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val notNull2 = iterWithNulls.requireNoNulls()
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failsWith<IllegalArgumentException> {
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// should throw an exception as we have a null
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notNull2.toList()
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}
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}
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test fun toStringJoinsNoMoreThanTheFirstTenElements() {
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assertEquals("0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...", fibonacci().makeString(limit = 10))
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assertEquals("13, 21, 34, 55, 89, 144, 233, 377, 610, 987, ...", fibonacci().filter { it > 10 }.makeString(limit = 10))
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assertEquals("144, 233, 377, 610, 987", fibonacci().filter { it > 100 }.takeWhile { it < 1000 }.makeString())
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}
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}
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