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Fn3.java
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Fn3.java
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// Copyright 2015-04-13 PlanBase Inc. & Glen Peterson
//
// Licensed 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.organicdesign.fp.function;
import java.util.HashMap;
import java.util.Map;
import org.jetbrains.annotations.NotNull;
import org.organicdesign.fp.oneOf.Option;
import org.organicdesign.fp.tuple.Tuple3;
/** A three-argument, exception-safe functional interface. */
@FunctionalInterface
public interface Fn3<A,B,C,R> {
/** Implement this one method and you don't have to worry about checked exceptions. */
R applyEx(A a, B b, C c) throws Exception;
/**
* The class that takes a consumer as an argument uses this convenience method so that it
* doesn't have to worry about checked exceptions either.
*/
default R apply(A a, B b, C c) {
try {
return applyEx(a, b, c);
} catch (RuntimeException re) {
throw re;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
/**
* Use only on pure functions with no side effects. Wrap an expensive function with this and for each input
* value, the output will only be computed once. Subsequent calls with the same input will return identical output
* very quickly. Please note that the parameters to f need to implement equals() and hashCode() correctly
* for this to work correctly and quickly. Also, make sure your domain is very small! This function uses O(n^3)
* memory.
*/
static <A,B,C,Z> @NotNull Fn3<A,B,C,Z> memoize(@NotNull Fn3<A,B,C,Z> f) {
return new Fn3<>() {
private final Map<Tuple3<A,B,C>,Option<Z>> map = new HashMap<>();
@Override
public synchronized Z applyEx(A a, B b, C c) throws Exception {
Tuple3<A,B,C> t3 = Tuple3.of(a, b, c);
Option<Z> val = map.get(t3);
if (val != null) { return val.get(); }
Z ret = f.applyEx(a, b, c);
map.put(t3, Option.some(ret));
return ret;
}
};
}
}