001 /*
002 * Java Genetic Algorithm Library (jenetics-1.6.0).
003 * Copyright (c) 2007-2014 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: 2014-02-27 $</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 * @deprecated Will be removed.
092 */
093 @Deprecated
094 public static final Function<String, Integer64>
095 StringToInteger64 = new Function<String, Integer64>() {
096 @Override public Integer64 apply(final String value) {
097 return Integer64.valueOf(value);
098 }
099 };
100
101 /**
102 * Convert a string to a float. If the string can't be converted, an
103 * {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
104 * method.
105 */
106 public static final Function<String, Float>
107 StringToFloat = new Function<String, Float>() {
108 @Override public Float apply(final String value) {
109 return Float.parseFloat(value);
110 }
111 };
112
113 /**
114 * Convert a string to a double. If the string can't be converted, an
115 * {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
116 * method.
117 */
118 public static final Function<String, Double>
119 StringToDouble = new Function<String, Double>() {
120 @Override public Double apply(final String value) {
121 return Double.parseDouble(value);
122 }
123 };
124
125 /**
126 * Convert a string to a Float64. If the string can't be converted, an
127 * {@link NumberFormatException} is throws by the {@link Function#apply(Object)}
128 * method.
129 *
130 * @deprecated Will be removed.
131 */
132 @Deprecated
133 public static final Function<String, Float64>
134 StringToFloat64 = new Function<String, Float64>() {
135 @Override public Float64 apply(final String value) {
136 return Float64.valueOf(value);
137 }
138 };
139
140 /**
141 * Convert a {@link Float64} value to a {@link Double} value.
142 *
143 * @deprecated Will be removed.
144 */
145 @Deprecated
146 public static final Function<Float64, Double>
147 Float64ToDouble = new Function<Float64, Double>() {
148 @Override public Double apply(final Float64 value) {
149 return value.doubleValue();
150 }
151 };
152
153 /**
154 * Convert a {@link Double} value to a {@link Float64} value.
155 *
156 * @deprecated Will be removed.
157 */
158 @Deprecated
159 public static final Function<Double, Float64>
160 DoubleToFloat64 = new Function<Double, Float64>() {
161 @Override public Float64 apply(final Double value) {
162 return Float64.valueOf(value);
163 }
164 };
165
166 /**
167 * Convert a {@link Integer64} value to a {@link Long} value.
168 *
169 * @deprecated Will be removed.
170 */
171 @Deprecated
172 public static final Function<Integer64, Long>
173 Integer64ToLong = new Function<Integer64, Long>() {
174 @Override public Long apply(final Integer64 value) {
175 return value.longValue();
176 }
177 };
178
179 /**
180 * Convert a {link Long} value to a {@link Integer64} value.
181 *
182 * @deprecated Will be removed.
183 */
184 @Deprecated
185 public static final Function<Long, Integer64>
186 LongToInteger64 = new Function<Long, Integer64>() {
187 @Override public Integer64 apply(final Long value) {
188 return Integer64.valueOf(value);
189 }
190 };
191
192 /**
193 * A predicate which return {@code true} if an given value is {@code null}.
194 */
195 public static final Function<Object, Boolean>
196 Null = new Function<Object, Boolean>() {
197 @Override public Boolean apply(final Object object) {
198 return object == null ? Boolean.TRUE : Boolean.FALSE;
199 }
200 @Override public String toString() {
201 return format("%s", getClass().getSimpleName());
202 }
203 };
204
205 /**
206 * Return a predicate which negates the return value of the given predicate.
207 *
208 * @param <T> the value type to check.
209 * @param a the predicate to negate.
210 * @return a predicate which negates the return value of the given predicate.
211 * @throws NullPointerException if the given predicate is {@code null}.
212 */
213 public static <T> Function<T, Boolean> not(final Function<? super T, Boolean> a) {
214 requireNonNull(a);
215 return new Function<T, Boolean>() {
216 @Override public Boolean apply(final T object) {
217 return a.apply(object) ? Boolean.FALSE : Boolean.TRUE;
218 }
219 @Override public String toString() {
220 return format("%s[%s]", getClass().getSimpleName(), a);
221 }
222 };
223 }
224
225 /**
226 * Return a {@code and} combination of the given predicates.
227 *
228 * @param <T> the value type to check.
229 * @param a the first predicate
230 * @param b the second predicate
231 * @return a {@code and} combination of the given predicates.
232 * @throws NullPointerException if one of the given predicates is
233 * {@code null}.
234 */
235 public static <T> Function<T, Boolean> and(
236 final Function<? super T, Boolean> a,
237 final Function<? super T, Boolean> b
238 ) {
239 requireNonNull(a);
240 requireNonNull(b);
241 return new Function<T, Boolean>() {
242 @Override public Boolean apply(final T object) {
243 return a.apply(object) && b.apply(object);
244 }
245 @Override public String toString() {
246 return format("%s[%s, %s]", getClass().getSimpleName(), a, b);
247 }
248 };
249 }
250
251 /**
252 * Return a {@code or} combination of the given predicates.
253 *
254 * @param <T> the value type to check.
255 * @param a the first predicate
256 * @param b the second predicate
257 * @return a {@code and} combination of the given predicates.
258 * @throws NullPointerException if one of the given predicates is
259 * {@code null}.
260 */
261 public static <T> Function<T, Boolean> or(
262 final Function<? super T, Boolean> a,
263 final Function<? super T, Boolean> b
264 ) {
265 requireNonNull(a);
266 requireNonNull(b);
267 return new Function<T, Boolean>() {
268 @Override public Boolean apply(final T object) {
269 return a.apply(object) || b.apply(object);
270 }
271 @Override public String toString() {
272 return format(
273 "%s[%s, %s]",
274 getClass().getSimpleName(), a, b
275 );
276 }
277 };
278 }
279
280
281 private static final class Identity
282 implements Function<Object, Object>, Serializable
283 {
284 private static final long serialVersionUID = 1L;
285
286 @Override
287 public Object apply(final Object value) {
288 return value;
289 }
290 }
291
292 private static Function<Object, Object> IDENTITY = new Identity();
293
294 /**
295 * Return the identity function for the given type.
296 *
297 * @return the identity function for the given type.
298 */
299 @SuppressWarnings("unchecked")
300 public static <T> Function<T, T> Identity() {
301 return (Function<T, T>)IDENTITY;
302 }
303
304
305 public static <A, B, C> Function<A, C> compose(
306 final Function<A, B> f1,
307 final Function<B, C> f2
308 ) {
309 requireNonNull(f1, "Function 1");
310 requireNonNull(f2, "Function 2");
311
312 return new Function<A, C>() {
313 @Override public C apply(A value) {
314 return f2.apply(f1.apply(value));
315 }
316 };
317 }
318
319 public static <A, B, C, D> Function<A, D> compose(
320 final Function<A, B> f1,
321 final Function<B, C> f2,
322 final Function<C, D> f3
323 ) {
324 return compose(compose(f1, f2), f3);
325 }
326
327 public static <A, B, C, D, E> Function<A, E> compose(
328 final Function<A, B> f1,
329 final Function<B, C> f2,
330 final Function<C, D> f3,
331 final Function<D, E> f4
332 ) {
333 return compose(compose(compose(f1, f2), f3), f4);
334 }
335
336 public static <A, B, C, D, E, F> Function<A, F> compose(
337 final Function<A, B> f1,
338 final Function<B, C> f2,
339 final Function<C, D> f3,
340 final Function<D, E> f4,
341 final Function<E, F> f5
342 ) {
343 return compose(compose(compose(compose(f1, f2), f3), f4), f5);
344 }
345
346 }
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