KT-1653 Implemented map, flatMap, take, takeWhile, join, and toString for iterators, #KT-1653 Fixed

2012-03-28 15:55:27 +01:00
parent c68d9c62f6
commit ca4f552245
2 changed files with 173 additions and 51 deletions
@@ -0,0 +1,59 @@
+package iterators
+
+import kotlin.test.assertEquals
+import org.junit.Test
+
+class IteratorsTest {
+
+    private fun fibonacci(): java.util.Iterator<Int> {
+        // fibonacci terms
+        var index = 0; var a = 0; var b = 1
+        return iterate<Int> { when (index++) { 0 -> a; 1 -> b; else -> { val result = a + b; a = b; b = result; result } } }
+    }
+
+    Test fun filterAndTakeWhileExtractTheElementsWithinRange() {
+        assertEquals(arrayList(144, 233, 377, 610, 987), fibonacci().filter { it > 100 }.takeWhile { it < 1000 }.toList())
+    }
+
+    Test fun foldReducesTheFirstNElements() {
+        val sum = { (a: Int, b: Int) -> a + b }
+        assertEquals(arrayList(13, 21, 34, 55, 89).fold(0, sum), fibonacci().filter { it > 10 }.take(5).fold(0, sum))
+    }
+
+    Test fun takeExtractsTheFirstNElements() {
+        assertEquals(arrayList(0, 1, 1, 2, 3, 5, 8, 13, 21, 34), fibonacci().take(10).toList())
+    }
+
+    Test fun mapAndTakeWhileExtractTheTransformedElements() {
+        assertEquals(arrayList(0, 3, 3, 6, 9, 15), fibonacci().map { it * 3 }.takeWhile { (i: Int) -> i < 20 }.toList())
+    }
+
+    Test fun flatMapAndTakeExtractTheTransformedElements() {
+        fun intToBinaryDigits() = { (i: Int) ->
+            val binary = Integer.toBinaryString(i).sure()
+            var index = 0
+            iterate<Char> { if (index < binary.length()) binary.get(index++) else null }
+        }
+
+        val expected = arrayList(
+                      '0', // fibonacci(0) = 0
+                      '1', // fibonacci(1) = 1
+                      '1', // fibonacci(2) = 1
+                 '1', '0', // fibonacci(3) = 2
+                 '1', '1', // fibonacci(4) = 3
+            '1', '0', '1'  // fibonacci(5) = 5
+        )
+
+        assertEquals(expected, fibonacci().flatMap<Int, Char>(intToBinaryDigits()).take(10).toList())
+    }
+
+    Test fun joinConcatenatesTheFirstNElementsAboveAThreshold() {
+        assertEquals("13, 21, 34, 55, 89, ...", fibonacci().filter { it > 10 }.join(separator = ", ", limit = 5))
+    }
+
+    Test fun toStringJoinsNoMoreThanTheFirstTenElements() {
+        assertEquals("0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...", fibonacci().toString())
+        assertEquals("13, 21, 34, 55, 89, 144, 233, 377, 610, 987, ...", fibonacci().filter {  it > 10 }.toString())
+        assertEquals("144, 233, 377, 610, 987", fibonacci().filter { it > 100 }.takeWhile { it < 1000 }.toString())
+    }
+}