org.opencastproject.util.data.functions.Options Maven / Gradle / Ivy
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* Licensed to The Apereo Foundation under one or more contributor license
* agreements. See the NOTICE file distributed with this work for additional
* information regarding copyright ownership.
*
*
* The Apereo Foundation licenses this file to you under the Educational
* Community 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://opensource.org/licenses/ecl2.txt
*
* 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.opencastproject.util.data.functions;
import static org.opencastproject.util.data.Monadics.mlist;
import static org.opencastproject.util.data.Option.some;
import org.opencastproject.util.data.Effect;
import org.opencastproject.util.data.Function;
import org.opencastproject.util.data.Function2;
import org.opencastproject.util.data.Option;
import java.util.ArrayList;
import java.util.List;
/** {@link Option} related functions. */
public final class Options {
private Options() {
}
/** m (m a) -> m a */
public static Option join(Option> a) {
return a.bind(Functions.> identity());
}
public static Function, List> asList() {
return new Function, List>() {
@Override
public List apply(Option a) {
return a.list();
}
};
}
/** Returns some(message) if predicate is false, none otherwise. */
public static Option toOption(boolean predicate, String message) {
return predicate ? Option. none() : some(message);
}
/** Sequence a list of options. [Option a] -> Option [a] */
public static Option> sequenceOpt(List> as) {
final List seq = mlist(as).foldl(new ArrayList(), new Function2, Option, List>() {
@Override
public List apply(List sum, Option o) {
for (A a : o) {
sum.add(a);
return sum;
}
return sum;
}
});
return some(seq);
}
/** Apply effect e to the result of f which is then returned. */
public static Function> foreach(final Function> f,
final Effect e) {
return new Function>() {
@Override
public Option apply(A a) {
return (Option) f.apply(a).foreach(e);
}
};
}
}