01 /*
02 * Java Genetic Algorithm Library (jenetics-7.1.1).
03 * Copyright (c) 2007-2022 Franz Wilhelmstötter
04 *
05 * Licensed under the Apache License, Version 2.0 (the "License");
06 * you may not use this file except in compliance with the License.
07 * You may obtain a copy of the License at
08 *
09 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 * Author:
18 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
19 */
20 package io.jenetics.ext.grammar;
21
22 import static java.util.Objects.requireNonNull;
23
24 import java.util.random.RandomGenerator;
25
26 import io.jenetics.ext.grammar.Cfg.Rule;
27
28 /**
29 * Functional interface for selecting a {@link Cfg.Symbol} by its index within a
30 * rule. It is an abstraction of the <em>codon</em> values used for selecting
31 * the alternatives from a rule during the sentence generation.
32 *
33 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
34 * @since 7.1
35 * @version 7.1
36 */
37 @FunctionalInterface
38 public interface SymbolIndex {
39
40 /**
41 * Selects an index with the given upper {@code bound}, exclusively.
42 *
43 * @param rule the rule which requested the index
44 * @param bound the upper bound of the symbol index, exclusively
45 * @return the next symbol index
46 * @throws IllegalArgumentException if the given {@code bound} is smaller
47 * than one
48 */
49 int next(final Rule<?> rule, final int bound);
50
51 /**
52 * Create a new symbol-index object from the given random generator. This
53 * can be used for generating random sentences of derivation-trees.
54 *
55 * @param random the random generator used for generating the sentences
56 * @return a new symbol-index object from the given random generator
57 * @throws NullPointerException if the given {@code random} generator is
58 * {@code null}
59 */
60 static SymbolIndex of(final RandomGenerator random) {
61 requireNonNull(random);
62 return (rule, bound) -> random.nextInt(bound);
63 }
64
65 }
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