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/* Copyright (C) 2013-2020 TU Dortmund
* This file is part of LearnLib, http://www.learnlib.de/.
*
* 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 de.learnlib.api;
import de.learnlib.api.exception.SULException;
/**
* Interface for a system under learning (SUL) that can make single steps.
*
* @param
* input symbols
* @param
* output symbols
*
* @author falkhowar
* @author Malte Isberner
*/
public interface SUL {
/**
* setup SUL.
*/
void pre();
/**
* shut down SUL.
*/
void post();
/**
* make one step on the SUL.
*
* @param in
* input to the SUL
*
* @return output of SUL
*
* @throws SULException
* if the input symbol cannot be executed on the SUL
*/
O step(I in);
/**
* Returns whether this SUL is capable of {@link #fork() forking}.
*
* @return {@code true} if this SUL can be forked, {@code false} otherwise
*
* @see #fork()
*/
default boolean canFork() {
return false;
}
/**
* Forks this SUL, if possible. The fork of a SUL is a copy which behaves exactly the same as this SUL. This method
* should always return a reseted SUL, regardless of whether this call is made between a call to {@link #pre()} and
* {@link #post()}.
*
* If {@link #canFork()} returns {@code true}, this method must return a non-{@code null} object, which should
* behave exactly like this SUL (in particular, it must be forkable as well). Otherwise, a {@link
* UnsupportedOperationException} must be thrown.
*
* Implementation note: if resetting a SUL changes the internal state of this object in a non-trivial way (e.g.,
* incrementing a counter to ensure independent sessions), care must be taken that forks of this SUL manipulate the
* same internal state.
*
* @return a fork of this SUL.
*
* @throws UnsupportedOperationException
* if this SUL can't be forked.
*/
default SUL fork() {
throw new UnsupportedOperationException();
}
}