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+ Adding basic implementation of a `TriFunction`, which Java does not have
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src/main/java/com/ginsberg/gatherers4j/FoldIndexedGatherer.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,70 @@ | ||
| /* | ||
| * Copyright 2025 Todd Ginsberg | ||
| * | ||
| * 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. | ||
| */ | ||
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| package com.ginsberg.gatherers4j; | ||
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| import org.jspecify.annotations.Nullable; | ||
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| import java.util.function.BiConsumer; | ||
| import java.util.function.Supplier; | ||
| import java.util.stream.Gatherer; | ||
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| import static com.ginsberg.gatherers4j.GathererUtils.mustNotBeNull; | ||
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| public class FoldIndexedGatherer<INPUT extends @Nullable Object, OUTPUT extends @Nullable Object> | ||
| implements Gatherer<INPUT, FoldIndexedGatherer.State<OUTPUT>, OUTPUT> { | ||
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| private final TriFunction<Long, OUTPUT, INPUT, OUTPUT> foldFunction; | ||
| private final Supplier<OUTPUT> initialValue; | ||
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| FoldIndexedGatherer( | ||
| final Supplier<OUTPUT> initialValue, | ||
| final TriFunction<Long, OUTPUT, INPUT, OUTPUT> foldFunction | ||
| ) { | ||
| mustNotBeNull(initialValue, "Initial value supplier must not be null"); | ||
| mustNotBeNull(foldFunction, "Fold function must not be null"); | ||
| this.foldFunction = foldFunction; | ||
| this.initialValue = initialValue; | ||
| } | ||
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| @Override | ||
| public Supplier<State<OUTPUT>> initializer() { | ||
| return () -> new State<>(initialValue.get()); | ||
| } | ||
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| @Override | ||
| public Integrator<State<OUTPUT>, INPUT, OUTPUT> integrator() { | ||
| return Integrator.ofGreedy((state, element, downstream) -> { | ||
| state.carriedValue = foldFunction.apply(state.index++, state.carriedValue, element); | ||
| return !downstream.isRejecting(); | ||
| }); | ||
| } | ||
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| @Override | ||
| public BiConsumer<State<OUTPUT>, Downstream<? super OUTPUT>> finisher() { | ||
| return (outputState, downstream) -> downstream.push(outputState.carriedValue); | ||
| } | ||
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| public static class State<OUTPUT> { | ||
| @Nullable | ||
| OUTPUT carriedValue; | ||
| long index; | ||
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| private State(@Nullable final OUTPUT initialValue) { | ||
| carriedValue = initialValue; | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,35 @@ | ||
| /* | ||
| * Copyright 2025 Todd Ginsberg | ||
| * | ||
| * 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. | ||
| */ | ||
|
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| package com.ginsberg.gatherers4j; | ||
|
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| import org.jspecify.annotations.Nullable; | ||
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| @FunctionalInterface | ||
| public interface TriFunction< | ||
| A extends @Nullable Object, | ||
| B extends @Nullable Object, | ||
| C extends @Nullable Object, | ||
| R extends @Nullable Object> { | ||
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| /// Applies this function to the given arguments | ||
| /// | ||
| /// @param a the first function argument | ||
| /// @param b the second function argument | ||
| /// @param c the third function argument | ||
| /// @return the function result | ||
| R apply(A a, B b, C c); | ||
| } |
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