Author: hlship
Date: Wed May 26 01:57:45 2010
New Revision: 948286
URL: http://svn.apache.org/viewvc?rev=948286&view=rev
Log:
Add a new Reducer interface and F.reduce().
Added:
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Reducer.java
- copied, changed from r948279,
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Predicate.java
Modified:
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/F.java
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Predicate.java
tapestry/tapestry5/trunk/tapestry-ioc/src/test/java/org/apache/tapestry5/ioc/util/func/FuncTest.java
Modified:
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/F.java
URL:
http://svn.apache.org/viewvc/tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/F.java?rev=948286&r1=948285&r2=948286&view=diff
==============================================================================
---
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/F.java
(original)
+++
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/F.java
Wed May 26 01:57:45 2010
@@ -190,6 +190,7 @@ public class F
return isNull.invert();
}
+ /** Returns a Mapper that ignores its input value and always returns a
predetermined result. */
public static <S, T> Mapper<S, T> always(final T fixedResult)
{
return new AbstractMapper<S, T>()
@@ -202,7 +203,7 @@ public class F
}
/**
- * Coercion factory that combines a Predicate with two {...@link Mapper}s;
evaluating the predicate selects one of the
+ * Mapper factory that combines a Predicate with two {...@link Mapper}s;
evaluating the predicate selects one of the
* two mappers.
*
* @param predicate
@@ -244,6 +245,7 @@ public class F
return select(predicate, ifAccepted, rejectedMapper);
}
+ /** The identity mapper simply returns the input unchanged. */
public static <S> Mapper<S, S> identity()
{
return new AbstractMapper<S, S>()
@@ -255,7 +257,7 @@ public class F
};
}
- /** Allows Coercion to boolean to be used as a Predicate. */
+ /** Allows Mapper that maps to boolean to be used as a Predicate. */
public static <S> Predicate<S> toPredicate(final Mapper<S, Boolean> mapper)
{
return new AbstractPredicate<S>()
@@ -266,4 +268,27 @@ public class F
};
};
}
+
+ public static <A, T> A reduce(Reducer<A, T> reducer, A initial,
Collection<T> values)
+ {
+ Defense.notNull(reducer, "reducer");
+ Defense.notNull(values, "values");
+
+ A accumulator = initial;
+
+ for (T value : values)
+ {
+ accumulator = reducer.reduce(accumulator, value);
+ }
+
+ return accumulator;
+ }
+
+ public static Reducer<Integer, Integer> SUM_INTS = new Reducer<Integer,
Integer>()
+ {
+ public Integer reduce(Integer accumulator, Integer value)
+ {
+ return accumulator + value;
+ };
+ };
}
Modified:
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Predicate.java
URL:
http://svn.apache.org/viewvc/tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Predicate.java?rev=948286&r1=948285&r2=948286&view=diff
==============================================================================
---
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Predicate.java
(original)
+++
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Predicate.java
Wed May 26 01:57:45 2010
@@ -17,8 +17,12 @@ package org.apache.tapestry5.ioc.util.fu
/**
* Used when filtering a collection of objects of a given type; the predicate
is passed
* each object in turn, and returns true to include the object in the result
collection.
+ * <p>
+ * The {...@link F} class includes a number of Predicate factory methods.
*
* @since 5.2.0
+ * @see F#filter(Predicate, java.util.List)
+ * @see F#remove(Predicate, java.util.List)
*/
public interface Predicate<T>
{
Copied:
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Reducer.java
(from r948279,
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Predicate.java)
URL:
http://svn.apache.org/viewvc/tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Reducer.java?p2=tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Reducer.java&p1=tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Predicate.java&r1=948279&r2=948286&rev=948286&view=diff
==============================================================================
---
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Predicate.java
(original)
+++
tapestry/tapestry5/trunk/tapestry-ioc/src/main/java/org/apache/tapestry5/ioc/util/func/Reducer.java
Wed May 26 01:57:45 2010
@@ -15,23 +15,14 @@
package org.apache.tapestry5.ioc.util.func;
/**
- * Used when filtering a collection of objects of a given type; the predicate
is passed
- * each object in turn, and returns true to include the object in the result
collection.
+ * A reducer takes an accumulator value and a single value from a collection
and computes a new
+ * accumulator value.
+ * <A> type of accumulator
+ * <T> type of collection value
*
* @since 5.2.0
*/
-public interface Predicate<T>
+public interface Reducer<A, T>
{
- /**
- * Examines the object and determines whether to accept or reject it.
- *
- * @return true to accept, false to reject
- */
- boolean accept(T object);
-
- Predicate<T> invert();
-
- Predicate<T> and(Predicate<? super T> right);
-
- Predicate<T> or(Predicate<? super T> right);
+ A reduce(A accumulator, T value);
}
Modified:
tapestry/tapestry5/trunk/tapestry-ioc/src/test/java/org/apache/tapestry5/ioc/util/func/FuncTest.java
URL:
http://svn.apache.org/viewvc/tapestry/tapestry5/trunk/tapestry-ioc/src/test/java/org/apache/tapestry5/ioc/util/func/FuncTest.java?rev=948286&r1=948285&r2=948286&view=diff
==============================================================================
---
tapestry/tapestry5/trunk/tapestry-ioc/src/test/java/org/apache/tapestry5/ioc/util/func/FuncTest.java
(original)
+++
tapestry/tapestry5/trunk/tapestry-ioc/src/test/java/org/apache/tapestry5/ioc/util/func/FuncTest.java
Wed May 26 01:57:45 2010
@@ -226,4 +226,12 @@ public class FuncTest extends TestBase
assertEquals(isNull.accept("foo"), false);
assertEquals(isNotNull.accept("bar"), true);
}
+
+ @Test
+ public void reduce()
+ {
+ int total = F.reduce(F.SUM_INTS, 0, F.map(stringToLength, "Mary",
"had", "a", "little", "lamb"));
+
+ assertEquals(total, 18);
+ }
}
