001 /*
002 * Java Genetic Algorithm Library (jenetics-1.5.0).
003 * Copyright (c) 2007-2013 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 *
017 * Author:
018 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmx.at)
019 */
020 package org.jenetics.util;
021
022 import static java.lang.String.format;
023 import static java.util.Objects.requireNonNull;
024
025 import java.io.Serializable;
026 import java.util.Objects;
027
028 import org.jscience.mathematics.number.Float64;
029 import org.jscience.mathematics.number.Integer64;
030
031 /**
032 * This class contains some short general purpose functions.
033 *
034 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
035 * @since 1.0
036 * @version 1.0 — <em>$Date: 2013-12-02 $</em>
037 */
038 public final class functions extends StaticObject {
039 private functions() {}
040
041 /**
042 * Convert an object to a string by calling the objects {@link Object#toString()}
043 * method.
044 */
045 public static final Function<Object, String>
046 ObjectToString = new Function<Object, String>() {
047 @Override public String apply(final Object value) {
048 return Objects.toString(value);
049 }
050 };
051
052 /**
053 * Convert a string value to its length.
054 */
055 public static final Function<String, Integer>
056 StringLength = new Function<String, Integer>() {
057 @Override public Integer apply(final String value) {
058 return value.length();
059 }
060 };
061
062 /**
063 * Convert a string to an integer. If the string can't be converted, an
064 * {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
065 * method.
066 */
067 public static final Function<String, Integer>
068 StringToInteger = new Function<String, Integer>() {
069 @Override public Integer apply(final String value) {
070 return Integer.parseInt(value);
071 }
072 };
073
074 /**
075 * Convert a string to a long. If the string can't be converted, an
076 * {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
077 * method.
078 */
079 public static final Function<String, Long>
080 StringToLong = new Function<String, Long>() {
081 @Override public Long apply(final String value) {
082 return Long.parseLong(value);
083 }
084 };
085
086 /**
087 * Convert a string to an Integer64. If the string can't be converted, an
088 * {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
089 * method.
090 */
091 public static final Function<String, Integer64>
092 StringToInteger64 = new Function<String, Integer64>() {
093 @Override public Integer64 apply(final String value) {
094 return Integer64.valueOf(value);
095 }
096 };
097
098 /**
099 * Convert a string to a float. If the string can't be converted, an
100 * {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
101 * method.
102 */
103 public static final Function<String, Float>
104 StringToFloat = new Function<String, Float>() {
105 @Override public Float apply(final String value) {
106 return Float.parseFloat(value);
107 }
108 };
109
110 /**
111 * Convert a string to a double. If the string can't be converted, an
112 * {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
113 * method.
114 */
115 public static final Function<String, Double>
116 StringToDouble = new Function<String, Double>() {
117 @Override public Double apply(final String value) {
118 return Double.parseDouble(value);
119 }
120 };
121
122 /**
123 * Convert a string to a Float64. If the string can't be converted, an
124 * {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
125 * method.
126 */
127 public static final Function<String, Float64>
128 StringToFloat64 = new Function<String, Float64>() {
129 @Override public Float64 apply(final String value) {
130 return Float64.valueOf(value);
131 }
132 };
133
134 /**
135 * Convert a {@link Float64} value to a {@link Double} value.
136 */
137 public static final Function<Float64, Double>
138 Float64ToDouble = new Function<Float64, Double>() {
139 @Override public Double apply(final Float64 value) {
140 return value.doubleValue();
141 }
142 };
143
144 /**
145 * Convert a {@link Double} value to a {@link Float64} value.
146 */
147 public static final Function<Double, Float64>
148 DoubleToFloat64 = new Function<Double, Float64>() {
149 @Override public Float64 apply(final Double value) {
150 return Float64.valueOf(value);
151 }
152 };
153
154 /**
155 * Convert a {@link Integer64} value to a {@link Long} value.
156 */
157 public static final Function<Integer64, Long>
158 Integer64ToLong = new Function<Integer64, Long>() {
159 @Override public Long apply(final Integer64 value) {
160 return value.longValue();
161 }
162 };
163
164 /**
165 * Convert a {link Long} value to a {@link Integer64} value.
166 */
167 public static final Function<Long, Integer64>
168 LongToInteger64 = new Function<Long, Integer64>() {
169 @Override public Integer64 apply(final Long value) {
170 return Integer64.valueOf(value);
171 }
172 };
173
174 /**
175 * A predicate which return {@code true} if an given value is {@code null}.
176 */
177 public static final Function<Object, Boolean>
178 Null = new Function<Object, Boolean>() {
179 @Override public Boolean apply(final Object object) {
180 return object == null ? Boolean.TRUE : Boolean.FALSE;
181 }
182 @Override public String toString() {
183 return format("%s", getClass().getSimpleName());
184 }
185 };
186
187 /**
188 * Return a predicate which negates the return value of the given predicate.
189 *
190 * @param <T> the value type to check.
191 * @param a the predicate to negate.
192 * @return a predicate which negates the return value of the given predicate.
193 * @throws NullPointerException if the given predicate is {@code null}.
194 */
195 public static <T> Function<T, Boolean> not(final Function<? super T, Boolean> a) {
196 requireNonNull(a);
197 return new Function<T, Boolean>() {
198 @Override public Boolean apply(final T object) {
199 return a.apply(object) ? Boolean.FALSE : Boolean.TRUE;
200 }
201 @Override public String toString() {
202 return format("%s[%s]", getClass().getSimpleName(), a);
203 }
204 };
205 }
206
207 /**
208 * Return a {@code and} combination of the given predicates.
209 *
210 * @param <T> the value type to check.
211 * @param a the first predicate
212 * @param b the second predicate
213 * @return a {@code and} combination of the given predicates.
214 * @throws NullPointerException if one of the given predicates is
215 * {@code null}.
216 */
217 public static <T> Function<T, Boolean> and(
218 final Function<? super T, Boolean> a,
219 final Function<? super T, Boolean> b
220 ) {
221 requireNonNull(a);
222 requireNonNull(b);
223 return new Function<T, Boolean>() {
224 @Override public Boolean apply(final T object) {
225 return a.apply(object) && b.apply(object);
226 }
227 @Override public String toString() {
228 return format("%s[%s, %s]", getClass().getSimpleName(), a, b);
229 }
230 };
231 }
232
233 /**
234 * Return a {@code or} combination of the given predicates.
235 *
236 * @param <T> the value type to check.
237 * @param a the first predicate
238 * @param b the second predicate
239 * @return a {@code and} combination of the given predicates.
240 * @throws NullPointerException if one of the given predicates is
241 * {@code null}.
242 */
243 public static <T> Function<T, Boolean> or(
244 final Function<? super T, Boolean> a,
245 final Function<? super T, Boolean> b
246 ) {
247 requireNonNull(a);
248 requireNonNull(b);
249 return new Function<T, Boolean>() {
250 @Override public Boolean apply(final T object) {
251 return a.apply(object) || b.apply(object);
252 }
253 @Override public String toString() {
254 return format(
255 "%s[%s, %s]",
256 getClass().getSimpleName(), a, b
257 );
258 }
259 };
260 }
261
262
263 private static final class Identity
264 implements Function<Object, Object>, Serializable
265 {
266 private static final long serialVersionUID = 1L;
267
268 @Override
269 public Object apply(final Object value) {
270 return value;
271 }
272 }
273
274 private static Function<Object, Object> IDENTITY = new Identity();
275
276 /**
277 * Return the identity function for the given type.
278 *
279 * @return the identity function for the given type.
280 */
281 @SuppressWarnings("unchecked")
282 public static <T> Function<T, T> Identity() {
283 return (Function<T, T>)IDENTITY;
284 }
285
286
287 public static <A, B, C> Function<A, C> compose(
288 final Function<A, B> f1,
289 final Function<B, C> f2
290 ) {
291 requireNonNull(f1, "Function 1");
292 requireNonNull(f2, "Function 2");
293
294 return new Function<A, C>() {
295 @Override public C apply(A value) {
296 return f2.apply(f1.apply(value));
297 }
298 };
299 }
300
301 public static <A, B, C, D> Function<A, D> compose(
302 final Function<A, B> f1,
303 final Function<B, C> f2,
304 final Function<C, D> f3
305 ) {
306 return compose(compose(f1, f2), f3);
307 }
308
309 public static <A, B, C, D, E> Function<A, E> compose(
310 final Function<A, B> f1,
311 final Function<B, C> f2,
312 final Function<C, D> f3,
313 final Function<D, E> f4
314 ) {
315 return compose(compose(compose(f1, f2), f3), f4);
316 }
317
318 public static <A, B, C, D, E, F> Function<A, F> compose(
319 final Function<A, B> f1,
320 final Function<B, C> f2,
321 final Function<C, D> f3,
322 final Function<D, E> f4,
323 final Function<E, F> f5
324 ) {
325 return compose(compose(compose(compose(f1, f2), f3), f4), f5);
326 }
327
328 }
329
330
331
332
333
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