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Posted to server-dev@james.apache.org by bt...@apache.org on 2016/09/29 10:51:56 UTC

[06/12] james-project git commit: JAMES-1781 Introduce FunctionGenerator

JAMES-1781 Introduce FunctionGenerator

A function generator is a function that produces an other function.
We can compose the result of several FunctionGenerator so that they end up producing only one function.


Project: http://git-wip-us.apache.org/repos/asf/james-project/repo
Commit: http://git-wip-us.apache.org/repos/asf/james-project/commit/50e3ab58
Tree: http://git-wip-us.apache.org/repos/asf/james-project/tree/50e3ab58
Diff: http://git-wip-us.apache.org/repos/asf/james-project/diff/50e3ab58

Branch: refs/heads/master
Commit: 50e3ab5844d6678c99210b08af588dfc69b1b24d
Parents: 55116a7
Author: Benoit Tellier <bt...@linagora.com>
Authored: Thu Jun 30 12:38:16 2016 +0700
Committer: Benoit Tellier <bt...@linagora.com>
Committed: Thu Sep 29 12:48:14 2016 +0200

----------------------------------------------------------------------
 .../apache/james/util/FunctionGenerator.java    | 29 ++++++++++
 .../james/util/FunctionGeneratorTest.java       | 58 ++++++++++++++++++++
 2 files changed, 87 insertions(+)
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http://git-wip-us.apache.org/repos/asf/james-project/blob/50e3ab58/server/container/util-java8/src/main/java/org/apache/james/util/FunctionGenerator.java
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diff --git a/server/container/util-java8/src/main/java/org/apache/james/util/FunctionGenerator.java b/server/container/util-java8/src/main/java/org/apache/james/util/FunctionGenerator.java
new file mode 100644
index 0000000..2342360
--- /dev/null
+++ b/server/container/util-java8/src/main/java/org/apache/james/util/FunctionGenerator.java
@@ -0,0 +1,29 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.util;
+
+import java.util.function.Function;
+
+@FunctionalInterface
+public interface FunctionGenerator<A, R> extends Function<A, Function<R, R>> {
+    default FunctionGenerator<A, R> composeGeneratedFunctions(FunctionGenerator<A, R> other) {
+        return a -> apply(a).compose(other.apply(a));
+    }
+}
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/james-project/blob/50e3ab58/server/container/util-java8/src/test/java/org/apache/james/util/FunctionGeneratorTest.java
----------------------------------------------------------------------
diff --git a/server/container/util-java8/src/test/java/org/apache/james/util/FunctionGeneratorTest.java b/server/container/util-java8/src/test/java/org/apache/james/util/FunctionGeneratorTest.java
new file mode 100644
index 0000000..9a7da21
--- /dev/null
+++ b/server/container/util-java8/src/test/java/org/apache/james/util/FunctionGeneratorTest.java
@@ -0,0 +1,58 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.util;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.function.Function;
+
+import org.junit.Test;
+
+public class FunctionGeneratorTest {
+
+    @Test
+    public void composeGeneratedFunctionsShouldProduceTheCompositionOfBothOperations() {
+        FunctionGenerator<Integer, Integer> generateAddition = i -> (j -> j + i);
+
+        Function<Integer, Integer> addSix = generateAddition.composeGeneratedFunctions(generateAddition).apply(3);
+
+        assertThat(addSix.apply(42)).isEqualTo(48);
+    }
+
+    @Test
+    public void composeGeneratedFunctionsShouldProduceTheCompositionOfBothOperationsWithDifferentArguments() {
+        FunctionGenerator<Integer, Integer> generateAddition = i -> (j -> j + i);
+        FunctionGenerator<Integer, Integer> generateDoubleAddition = i -> (j -> j + 2 * i);
+
+        Function<Integer, Integer> addNine = generateAddition.composeGeneratedFunctions(generateDoubleAddition).apply(3);
+
+        assertThat(addNine.apply(42)).isEqualTo(51);
+    }
+
+    @Test
+    public void composeGeneratedFunctionsShouldReturnSameResultWhenOperationsCommute() {
+        FunctionGenerator<Integer, Integer> generateAddition = i -> (j -> j + i);
+        FunctionGenerator<Integer, Integer> generateDoubleAddition = i -> (j -> j + 2 * i);
+
+        Function<Integer, Integer> addNine = generateDoubleAddition.composeGeneratedFunctions(generateAddition).apply(3);
+
+        assertThat(addNine.apply(42)).isEqualTo(51);
+    }
+}


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