Impl : Impl Filter And TestCode

myeonginwoo · Dec 15, 2016 · 1c01166 · 1c01166
1 parent ef3c4c7
commit 1c01166
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diff --git a/Either/src/main/kotlin/LeftProjection.kt b/Either/src/main/kotlin/LeftProjection.kt
@@ -10,4 +10,12 @@ class LeftProjection<out L,out R>(val value: L) {
     fun <X> map(f: (L) -> X): LeftProjection<X, R> {
         return LeftProjection(f(value))
     }
+
+    fun filter(predicate: (L) -> Boolean) : L? {
+        return if(predicate(value)) {
+            return value
+        } else {
+            null
+        }
+    }
 }
diff --git a/Either/src/main/kotlin/RightProjection.kt b/Either/src/main/kotlin/RightProjection.kt
@@ -10,4 +10,12 @@ class RightProjection<out L, out R>(val value: R) {
     fun <X : Any> map(f: (R) -> X): RightProjection<L, X> {
         return RightProjection(f(value))
     }
+
+    fun filter(predicate: (R) -> Boolean) : R? {
+        return if(predicate(value)) {
+            return value
+        } else {
+            null
+        }
+    }
 }
diff --git a/Either/src/test/kotlin/EitherTest.kt b/Either/src/test/kotlin/EitherTest.kt
@@ -50,4 +50,20 @@ class EitherTest {
         assertEquals(123.0, either.right?.map(Int::toDouble)?.get)
         assertEquals(246, either.right?.map { it * 2 }?.get)
     }
+
+    @Test fun leftFilterTest() {
+        val either: Either<String, Int> = Left("left")
+
+        assertEquals(either.left?.filter { it.length > 3 }, "left")
+        assertEquals(either.left?.filter { it.length > 5 }, null)
+        assertEquals(either.left?.filter { it.length > 5 } ?: "default", "default")
+    }
+
+    @Test fun rightFilterTest() {
+        val either: Either<String, Int> = Right(126)
+
+        assertEquals(either.right?.filter { it > 100 }, 126)
+        assertEquals(either.right?.filter { it < 100 }, null)
+        assertEquals(either.right?.filter { it < 100 } ?: -1, -1)
+    }
 }