Add Result.reduce(Result,BinaryOperator)
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4 changed files with 123 additions and 39 deletions
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@ -26,6 +26,7 @@ import net.kemitix.mon.maybe.Maybe;
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import java.util.Objects;
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import java.util.Objects;
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import java.util.concurrent.Callable;
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import java.util.concurrent.Callable;
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import java.util.function.BinaryOperator;
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import java.util.function.Consumer;
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import java.util.function.Consumer;
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import java.util.function.Function;
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import java.util.function.Function;
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import java.util.function.Predicate;
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import java.util.function.Predicate;
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@ -101,6 +102,11 @@ class Err<T> implements Result<T> {
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return this;
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return this;
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}
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}
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@Override
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public Result<T> reduce(final Result<T> identify, final BinaryOperator<T> operator) {
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return Result.error(error);
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}
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@Override
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@Override
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public boolean equals(final Object other) {
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public boolean equals(final Object other) {
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return other instanceof Err && Objects.equals(error, ((Err) other).error);
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return other instanceof Err && Objects.equals(error, ((Err) other).error);
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@ -25,10 +25,7 @@ import net.kemitix.mon.Functor;
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import net.kemitix.mon.maybe.Maybe;
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import net.kemitix.mon.maybe.Maybe;
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import java.util.concurrent.Callable;
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import java.util.concurrent.Callable;
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import java.util.function.Consumer;
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import java.util.function.*;
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import java.util.function.Function;
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import java.util.function.Predicate;
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import java.util.function.Supplier;
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/**
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/**
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* An Either type for holding a result or an error (Throwable).
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* An Either type for holding a result or an error (Throwable).
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@ -63,17 +60,6 @@ public interface Result<T> extends Functor<T, Result<?>> {
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return new Err<>(error);
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return new Err<>(error);
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}
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}
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/**
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* Create a Result for a success.
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*
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* @param value the value
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* @param <T> the type of the value
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* @return a successful Result
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*/
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static <T> Result<T> ok(final T value) {
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return new Success<>(value);
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}
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/**
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/**
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* Create a Result for a output of the Callable.
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* Create a Result for a output of the Callable.
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*
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*
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@ -90,6 +76,17 @@ public interface Result<T> extends Functor<T, Result<?>> {
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}
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}
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}
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}
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/**
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* Create a Result for a success.
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*
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* @param value the value
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* @param <T> the type of the value
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* @return a successful Result
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*/
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static <T> Result<T> ok(final T value) {
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return new Success<>(value);
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}
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/**
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/**
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* Creates a {@link Maybe} from the Result, where the Result is a success, then the Maybe will contain the value.
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* Creates a {@link Maybe} from the Result, where the Result is a success, then the Maybe will contain the value.
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*
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*
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@ -108,6 +105,15 @@ public interface Result<T> extends Functor<T, Result<?>> {
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}
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}
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}
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}
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/**
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* Extracts the successful value from the result, or throws the error Throwable.
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*
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* @return the value if a success
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* @throws Throwable the result is an error
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*/
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@SuppressWarnings("illegalthrows")
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T orElseThrow() throws Throwable;
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/**
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/**
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* Swaps the inner Result of a Maybe, so that a Result is on the outside.
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* Swaps the inner Result of a Maybe, so that a Result is on the outside.
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*
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*
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@ -122,6 +128,15 @@ public interface Result<T> extends Functor<T, Result<?>> {
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.flatMap(value -> Result.ok(Maybe.maybe(value)));
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.flatMap(value -> Result.ok(Maybe.maybe(value)));
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}
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}
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/**
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* Returns a new Result consisting of the result of applying the function to the contents of the Result.
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*
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* @param f the mapping function the produces a Result
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* @param <R> the type of the value withing the Result of the mapping function
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* @return a Result
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*/
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<R> Result<R> flatMap(Function<T, Result<R>> f);
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/**
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/**
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* Applies the function to the contents of a Maybe within the Result.
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* Applies the function to the contents of a Maybe within the Result.
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*
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*
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@ -131,7 +146,10 @@ public interface Result<T> extends Functor<T, Result<?>> {
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* @param <R> the type of the updated Result
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* @param <R> the type of the updated Result
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* @return a new Maybe within a Result
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* @return a new Maybe within a Result
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*/
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*/
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static <T, R> Result<Maybe<R>> flatMapMaybe(Result<Maybe<T>> maybeResult, Function<Maybe<T>, Result<Maybe<R>>> f) {
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static <T, R> Result<Maybe<R>> flatMapMaybe(
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final Result<Maybe<T>> maybeResult,
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final Function<Maybe<T>, Result<Maybe<R>>> f
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) {
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return maybeResult.flatMap(f);
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return maybeResult.flatMap(f);
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}
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}
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@ -149,15 +167,6 @@ public interface Result<T> extends Functor<T, Result<?>> {
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*/
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*/
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boolean isOkay();
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boolean isOkay();
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/**
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* Returns a new Result consisting of the result of applying the function to the contents of the Result.
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*
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* @param f the mapping function the produces a Result
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* @param <R> the type of the value withing the Result of the mapping function
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* @return a Result
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*/
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<R> Result<R> flatMap(Function<T, Result<R>> f);
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@Override
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@Override
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<R> Result<R> map(Function<T, R> f);
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<R> Result<R> map(Function<T, R> f);
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@ -177,15 +186,6 @@ public interface Result<T> extends Functor<T, Result<?>> {
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*/
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*/
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Result<Maybe<T>> maybe(Predicate<T> predicate);
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Result<Maybe<T>> maybe(Predicate<T> predicate);
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/**
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* Extracts the successful value from the result, or throws the error Throwable.
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*
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* @return the value if a success
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* @throws Throwable the result is an error
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*/
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@SuppressWarnings("illegalthrows")
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T orElseThrow() throws Throwable;
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/**
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/**
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* Provide the value within the Result, if it is a success, to the Consumer, and returns this Result.
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* Provide the value within the Result, if it is a success, to the Consumer, and returns this Result.
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*
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*
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@ -251,4 +251,16 @@ public interface Result<T> extends Functor<T, Result<?>> {
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* @return the Result or a new error Result
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* @return the Result or a new error Result
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*/
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*/
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Result<T> thenWith(Function<T, WithResultContinuation<T>> f);
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Result<T> thenWith(Function<T, WithResultContinuation<T>> f);
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/**
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* Reduce two Results of the same type into one using the reducing function provided.
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*
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* <p>If either Result is an error, then the reduce will return the error. If both are errors, then the error of
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* {@link this} Result will be returned.</p>
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*
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* @param identify the identify Result
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* @param operator the function to combine the values the Results
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* @return a Result containing the combination of the two Results
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*/
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Result<T> reduce(Result<T> identify, BinaryOperator<T> operator);
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}
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}
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@ -26,6 +26,7 @@ import net.kemitix.mon.maybe.Maybe;
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import java.util.Objects;
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import java.util.Objects;
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import java.util.concurrent.Callable;
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import java.util.concurrent.Callable;
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import java.util.function.BinaryOperator;
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import java.util.function.Consumer;
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import java.util.function.Consumer;
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import java.util.function.Function;
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import java.util.function.Function;
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import java.util.function.Predicate;
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import java.util.function.Predicate;
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@ -51,11 +52,6 @@ class Success<T> implements Result<T> {
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return true;
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return true;
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}
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}
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@Override
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public <R> Result<R> flatMap(final Function<T, Result<R>> f) {
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return f.apply(value);
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}
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@Override
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@Override
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public <R> Result<R> map(final Function<T, R> f) {
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public <R> Result<R> map(final Function<T, R> f) {
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return Result.ok(f.apply(value));
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return Result.ok(f.apply(value));
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@ -105,6 +101,16 @@ class Success<T> implements Result<T> {
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return f.apply(value).call(this);
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return f.apply(value).call(this);
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}
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}
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@Override
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public Result<T> reduce(final Result<T> identity, final BinaryOperator<T> operator) {
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return flatMap(a -> identity.flatMap(b -> Result.of(() -> operator.apply(a, b))));
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}
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@Override
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public <R> Result<R> flatMap(final Function<T, Result<R>> f) {
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return f.apply(value);
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}
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@Override
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@Override
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public boolean equals(final Object other) {
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public boolean equals(final Object other) {
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return other instanceof Success && Objects.equals(value, ((Success) other).value);
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return other instanceof Success && Objects.equals(value, ((Success) other).value);
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@ -671,6 +671,66 @@ public class ResultTest implements WithAssertions {
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);
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);
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}
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}
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@Test
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public void okayOkay_whenReduce_thenCombine() {
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//given
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final Result<Integer> result1 = Result.ok(1);
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final Result<Integer> result10 = Result.ok(10);
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//when
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final Result<Integer> result11 = result1.reduce(result10, (a, b) -> a + b);
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//then
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result11.match(
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success -> assertThat(success).isEqualTo(11),
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error -> fail("Not an error")
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);
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}
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@Test
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public void okayError_whenReduce_thenError() {
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//given
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final Result<Integer> result1 = Result.ok(1);
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final RuntimeException exception = new RuntimeException();
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final Result<Integer> result10 = Result.error(exception);
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//when
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final Result<Integer> result11 = result1.reduce(result10, (a, b) -> a + b);
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//then
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result11.match(
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success->fail("Not a success"),
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error -> assertThat(error).isSameAs(exception)
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);
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}
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@Test
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public void errorOkay_whenReduce_thenError() {
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//given
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final RuntimeException exception = new RuntimeException();
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final Result<Integer> result1 = Result.error(exception);
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final Result<Integer> result10 = Result.ok(10);
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//when
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final Result<Integer> result11 = result1.reduce(result10, (a, b) -> a + b);
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//then
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result11.match(
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success->fail("Not a success"),
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error -> assertThat(error).isSameAs(exception)
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);
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}
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@Test
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public void errorError_whenReduce_thenError() {
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//given
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final RuntimeException exception1 = new RuntimeException();
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final Result<Integer> result1 = Result.error(exception1);
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final RuntimeException exception10 = new RuntimeException();
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final Result<Integer> result10 = Result.error(exception10);
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//when
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final Result<Integer> result11 = result1.reduce(result10, (a, b) -> a + b);
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//then
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result11.match(
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success->fail("Not a success"),
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error -> assertThat(error).isSameAs(exception1)
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);
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}
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@RequiredArgsConstructor
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@RequiredArgsConstructor
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private static class UseCase {
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private static class UseCase {
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