| 1 | /* |
| 2 | * $Id: StepFunctions.java 562 2010-11-11 00:28:13Z PSpeed $ |
| 3 | * |
| 4 | * The Filament BSD license. |
| 5 | * |
| 6 | * Copyright (c) 2009-2010, the original author or authors |
| 7 | * |
| 8 | * Redistribution and use in source and binary forms, with or without |
| 9 | * modification, are permitted provided that the following conditions |
| 10 | * are met: |
| 11 | * |
| 12 | * 1) Redistributions of source code must retain the above copyright notice, |
| 13 | * this list of conditions and the following disclaimer. |
| 14 | * 2) Redistributions in binary form must reproduce the above copyright |
| 15 | * notice, this list of conditions and the following disclaimer in the |
| 16 | * documentation and/or other materials provided with the distribution. |
| 17 | * 3) Neither the names "Filament", "fgraph.org", "filamentgraph.org", nor the |
| 18 | * names of its contributors may be used to endorse or promote products |
| 19 | * derived from this software without specific prior written permission. |
| 20 | * |
| 21 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| 22 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 24 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE |
| 25 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 26 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 27 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 28 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 29 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 30 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 31 | * POSSIBILITY OF SUCH DAMAGE. |
| 32 | */ |
| 33 | |
| 34 | package org.fgraph.steps; |
| 35 | |
| 36 | import java.io.Serializable; |
| 37 | import java.util.*; |
| 38 | |
| 39 | import com.google.common.base.Function; |
| 40 | import com.google.common.base.Predicate; |
| 41 | import com.google.common.base.Predicates; |
| 42 | import com.google.common.collect.Iterables; |
| 43 | |
| 44 | |
| 45 | /** |
| 46 | * Set of utility functions that takes a starting step |
| 47 | * and produces zero to many result child steps. |
| 48 | * |
| 49 | * <p>Unless otherwise specified, all methods return serializable |
| 50 | * functions as long as they're given serializable parameters.</p> |
| 51 | * |
| 52 | * @version $Revision: 562 $ |
| 53 | * @author Paul Speed |
| 54 | */ |
| 55 | public class StepFunctions |
| 56 | { |
| 57 | /** |
| 58 | * Chains two functions together such the the individual element |
| 59 | * results from the first function are passed one at a time to the |
| 60 | * second function. All of the result Iterables are aggregated. |
| 61 | * Note: The argument ordering here is the opposite of of Functions.compose(). |
| 62 | */ |
| 63 | public static <A, B, C> StepFunction<A,C> chain( StepFunction<A,? extends B> f1, |
| 64 | StepFunction<B,C> f2 ) |
| 65 | { |
| 66 | return new ChainFunction<A,B,C>( f1, f2 ); |
| 67 | } |
| 68 | |
| 69 | /** |
| 70 | * Creates a function that concatenates the output of two other |
| 71 | * functions provided the common apply() input value. |
| 72 | */ |
| 73 | public static <S,T> StepFunction<S,T> concat( StepFunction<S,T> f1, StepFunction<S,T> f2 ) |
| 74 | { |
| 75 | return new ConcatFunction<S,T>( f1, f2 ); |
| 76 | } |
| 77 | |
| 78 | /** |
| 79 | * Creates a function that returns a fixed set of results no matter |
| 80 | * the input. |
| 81 | */ |
| 82 | public static <S,T> StepFunction<S,T> constant( T... values ) |
| 83 | { |
| 84 | List<T> list; |
| 85 | if( values == null ) |
| 86 | list = Collections.singletonList(null); |
| 87 | else |
| 88 | list = Arrays.asList(values); |
| 89 | return new ConstantFunction<S,T>(list); |
| 90 | } |
| 91 | |
| 92 | /** |
| 93 | * Creates a StepFunction adapter that transforms its input to a |
| 94 | * singleton Collection wrapped output using the supplied transform function. |
| 95 | * In other words, the actual processing is basically: |
| 96 | * Collections.singleton( transform.apply(value) ) |
| 97 | * |
| 98 | * <p>For the typical use-case, it is better to call the two-arg |
| 99 | * transform method that takes a delegate step function. This function |
| 100 | * is for composing chains where an input function may not be known |
| 101 | * or available at creation. There is additional overhead to create |
| 102 | * the one-per result singleton Iterables that is avoided in the two-arg |
| 103 | * version.</p> |
| 104 | */ |
| 105 | public static <S,T> StepFunction<S,T> transform( Function<S,T> transform ) |
| 106 | { |
| 107 | return new TransformDecorator<S,T>( transform ); |
| 108 | } |
| 109 | |
| 110 | /** |
| 111 | * Creates a StepFunction adapter that filters its input |
| 112 | * by passing it through the specified predicate. If the source |
| 113 | * passes the filter then it is wrapped in a Collection.sinleton() |
| 114 | * for return, otherwise an empty Iterable is returned. |
| 115 | * |
| 116 | * <p>For the typical use-case, it is better to call the two-arg |
| 117 | * filter() method that takes a delegate function. This function is |
| 118 | * for composing chains where an input function may not be known or |
| 119 | * or available at creation. There is additional overhead to create |
| 120 | * the one-per result singleton Iterables that is avoided in the two-arg |
| 121 | * version.</p> |
| 122 | */ |
| 123 | public static <T> StepFunction<T,T> filter( Predicate<T> filter ) |
| 124 | { |
| 125 | return new FilterDecorator<T>( filter ); |
| 126 | } |
| 127 | |
| 128 | /** |
| 129 | * Creates a function that adapts non-Step based results into |
| 130 | * root-level Step results. |
| 131 | */ |
| 132 | public static <T> StepFunction<T,Step<T>> wrapSteps() |
| 133 | { |
| 134 | return wrapSteps( (Step)null ); |
| 135 | } |
| 136 | |
| 137 | /** |
| 138 | * Creates a function that adapts non-Step based results into |
| 139 | * Step results with the supplied constant parent. |
| 140 | */ |
| 141 | public static <T> StepFunction<T,Step<T>> wrapSteps( Step parent ) |
| 142 | { |
| 143 | return transform( new WrapStep<T>( parent ) ); |
| 144 | } |
| 145 | |
| 146 | /** |
| 147 | * Creates a function that adapts the results of the specified |
| 148 | * delegate function into Steps using the specific constant |
| 149 | * parent. This is the preferred method of wrapping if another |
| 150 | * function is producing the non-step results, versus the single-arg |
| 151 | * wrapSteps which is useful at the head of a chain. |
| 152 | */ |
| 153 | public static <S,T> StepFunction<S,Step<T>> wrapSteps( StepFunction<S,T> delegate, Step parent ) |
| 154 | { |
| 155 | if( delegate == null ) |
| 156 | throw new IllegalArgumentException( "delegate cannot be null." ); |
| 157 | return transform( delegate, new WrapStep<T>( parent ) ); |
| 158 | } |
| 159 | |
| 160 | /** |
| 161 | * Creates a function that adapts the results of the specified |
| 162 | * delegate function into Steps using the Step supplied to apply() |
| 163 | * as the parent and its value as the value passed to the delegate |
| 164 | * function. This is useful for adapting non-step based functions |
| 165 | * into step-based chains where the full path is maintained. |
| 166 | */ |
| 167 | public static <S,T> StepFunction<Step<S>,Step<T>> adaptToSteps( StepFunction<S,T> delegate ) |
| 168 | { |
| 169 | return new StepAdapter<S,T>( delegate ); |
| 170 | } |
| 171 | |
| 172 | /** |
| 173 | * Creates a function that adapts a Step-based function for non-step |
| 174 | * usage by wrapping any applied objects in a DefaultStep and unwrapping |
| 175 | * any returned results. In other words, a function that takes a Step<S> and produces |
| 176 | * Step<T>'s can be adapted into a function that taks <S> and produces |
| 177 | * <T>. This effectively equivalent to unwrapSteps( chain( wrapSteps, delegate ) ) |
| 178 | */ |
| 179 | public static <S,T> StepFunction<S,T> adaptFromSteps( StepFunction<Step<S>,Step<T>> delegate ) |
| 180 | { |
| 181 | // Would be more efficient as a custom function. |
| 182 | return unwrapSteps( chain( StepFunctions.<S>wrapSteps(), delegate ) ); |
| 183 | } |
| 184 | |
| 185 | /** |
| 186 | * Creates a function that unwraps Step-based results into |
| 187 | * their component values. |
| 188 | */ |
| 189 | public static <T> StepFunction<Step<T>,T> unwrapSteps() |
| 190 | { |
| 191 | return transform( new UnwrapStep<T>() ); |
| 192 | } |
| 193 | |
| 194 | /** |
| 195 | * Creates a function that unwraps the results of the |
| 196 | * specified delegate function into the Step component values. |
| 197 | */ |
| 198 | public static <S,T> StepFunction<S,T> unwrapSteps( StepFunction<S,? extends Step<T>> delegate ) |
| 199 | { |
| 200 | return transform( delegate, new UnwrapStep<T>() ); |
| 201 | } |
| 202 | |
| 203 | /** |
| 204 | * Creates a StepFunction that filters the results of a delegate |
| 205 | * StepFunction using the supplied predicate filter. |
| 206 | */ |
| 207 | public static <S,T> StepFunction<S,T> filter( StepFunction<S,T> delegate, Predicate<? super T> filter ) |
| 208 | { |
| 209 | return new FilterFunction<S,T>( delegate, filter ); |
| 210 | } |
| 211 | |
| 212 | /** |
| 213 | * Creates a StepFunction that transforms the results of a delegate |
| 214 | * StepFunction using the supplied transform function. |
| 215 | */ |
| 216 | public static <A,B,C> StepFunction<A,C> transform( StepFunction<A,B> delegate, |
| 217 | Function<? super B,C> transform ) |
| 218 | { |
| 219 | // Note: in case you are wondering why: |
| 220 | // StepFunction<A,B> delegate, Function<? super B,C> transform |
| 221 | // instead of: |
| 222 | // StepFunction<A,? extends B> delegate, Function<B,C> transform |
| 223 | // |
| 224 | // It's because (I think) type resolution is not as smart |
| 225 | // as a human and is evaluating left to right. So once B |
| 226 | // is locked in with the first parameter, it doesn't matter if |
| 227 | // it could slide to support the second. |
| 228 | // |
| 229 | // This came up in StepDemo's all() method where we were calling |
| 230 | // transform with Stepfunction<Class,Method> and Function<Object,String>. |
| 231 | // Once <B> has been chosen as Method, there is no way to resolve |
| 232 | // things. In Google's Functions.compose() the ? extends B works |
| 233 | // because the parameters are in the reverse order. |
| 234 | return new TransformFunction<A,B,C>( delegate, transform ); |
| 235 | } |
| 236 | |
| 237 | /** |
| 238 | * Executes one of two delegate functions depending on the result |
| 239 | * of a predicate applied to the source object. |
| 240 | */ |
| 241 | public static <S,T> StepFunction<S,T> branch( Predicate<? super S> condition, |
| 242 | StepFunction<S,T> doTrue, |
| 243 | StepFunction<S,T> doFalse ) |
| 244 | { |
| 245 | return new ConditionalDelegator<S,T>( condition, doTrue, doFalse ); |
| 246 | } |
| 247 | |
| 248 | /** |
| 249 | * Convenience method that returns empty results for any source matching |
| 250 | * the supplied predicate and leaves those results out of any other |
| 251 | * adjacency sets. This is useful for pruning traversal hierarchies. |
| 252 | * This is the equivalent of branch( condition, null, delegate ) with a |
| 253 | * filter( branch, not condition ) |
| 254 | */ |
| 255 | public static <S,T extends S> StepFunction<S,T> prune( StepFunction<S,T> delegate, |
| 256 | Predicate<? super S> condition ) |
| 257 | { |
| 258 | StepFunction<S,T> b = branch( condition, null, delegate ); |
| 259 | return filter( b, Predicates.not(condition) ); |
| 260 | } |
| 261 | |
| 262 | /** |
| 263 | * Wraps the non-step elements of the specified Iterable |
| 264 | * in the DefaultStep with the supplied Step as a parent. |
| 265 | * This is used by other function implementations to adapt non-step |
| 266 | * based access into steps. |
| 267 | */ |
| 268 | public static <T> Iterable<Step<T>> doWrapSteps( Step parent, Iterable<T> children ) |
| 269 | { |
| 270 | return Iterables.transform( children, new WrapStep<T>(parent) ); |
| 271 | } |
| 272 | |
| 273 | /** |
| 274 | * Returns a raw function that can accept a single Step<T> and return |
| 275 | * a unwrapped single T value. |
| 276 | */ |
| 277 | public static <T> Function<Step<T>,T> unwrapStep() |
| 278 | { |
| 279 | return new UnwrapStep<T>(); |
| 280 | } |
| 281 | |
| 282 | /** |
| 283 | * Returns a raw function that can accept a single T and return |
| 284 | * a wrapped root Step<T> value. |
| 285 | */ |
| 286 | public static <T> Function<T,Step<T>> wrapStep() |
| 287 | { |
| 288 | return new WrapStep<T>(null); |
| 289 | } |
| 290 | |
| 291 | /** |
| 292 | * Returns a raw function that can accept a single T and return |
| 293 | * a wrapped Step<T> value with the specified parent. |
| 294 | */ |
| 295 | public static <T> Function<T,Step<T>> wrapStep( Step parent ) |
| 296 | { |
| 297 | return new WrapStep<T>(parent); |
| 298 | } |
| 299 | |
| 300 | private static class WrapStep<T> implements Function<T, Step<T>>, Serializable |
| 301 | { |
| 302 | static final long serialVersionUID = 1L; |
| 303 | |
| 304 | private Step parent; |
| 305 | |
| 306 | public WrapStep( Step parent ) |
| 307 | { |
| 308 | this.parent = parent; |
| 309 | } |
| 310 | |
| 311 | public Step<T> apply( T value ) |
| 312 | { |
| 313 | return new DefaultStep<T>( parent, value ); |
| 314 | } |
| 315 | |
| 316 | public String toString() |
| 317 | { |
| 318 | if( parent == null ) |
| 319 | return "WrapStep[]"; |
| 320 | return "WrapStep[parent=" + parent + "]"; |
| 321 | } |
| 322 | } |
| 323 | |
| 324 | private static class UnwrapStep<T> implements Function<Step<T>, T>, Serializable |
| 325 | { |
| 326 | static final long serialVersionUID = 1L; |
| 327 | |
| 328 | public UnwrapStep() |
| 329 | { |
| 330 | } |
| 331 | |
| 332 | public T apply( Step<T> step ) |
| 333 | { |
| 334 | return step.getValue(); |
| 335 | } |
| 336 | |
| 337 | public String toString() |
| 338 | { |
| 339 | return "UnwrapStep[]"; |
| 340 | } |
| 341 | } |
| 342 | |
| 343 | /** |
| 344 | * Wraps a delegate function to adapt it into a |
| 345 | * step-based StepFunction. |
| 346 | */ |
| 347 | private static class StepAdapter<S,T> implements StepFunction<Step<S>,Step<T>>, Serializable |
| 348 | { |
| 349 | static final long serialVersionUID = 1L; |
| 350 | |
| 351 | private Function<S,? extends Iterable<T>> delegate; |
| 352 | |
| 353 | public StepAdapter( Function<S,? extends Iterable<T>> delegate ) |
| 354 | { |
| 355 | if( delegate == null ) |
| 356 | throw new IllegalArgumentException( "delegate cannot be null." ); |
| 357 | this.delegate = delegate; |
| 358 | } |
| 359 | |
| 360 | public Iterable<Step<T>> apply( Step<S> step ) |
| 361 | { |
| 362 | // Wrap all of the results in steps with |
| 363 | // the passed step as parent |
| 364 | return Iterables.transform( delegate.apply(step.getValue()), |
| 365 | new WrapStep<T>(step) ); |
| 366 | } |
| 367 | |
| 368 | public String toString() |
| 369 | { |
| 370 | return "StepAdapter[" + delegate + "]"; |
| 371 | } |
| 372 | } |
| 373 | |
| 374 | private static class ConstantFunction<S,T> implements StepFunction<S,T>, Serializable |
| 375 | { |
| 376 | static final long serialVersionUID = 1L; |
| 377 | |
| 378 | private List<T> values; |
| 379 | |
| 380 | public ConstantFunction( List<T> values ) |
| 381 | { |
| 382 | this.values = values; |
| 383 | } |
| 384 | |
| 385 | public Iterable<T> apply( S object ) |
| 386 | { |
| 387 | return values; |
| 388 | } |
| 389 | |
| 390 | public String toString() |
| 391 | { |
| 392 | return "Constant[" + values + "]"; |
| 393 | } |
| 394 | } |
| 395 | |
| 396 | /** |
| 397 | * Executes a delegate function based on the result of a Predicate. |
| 398 | * Either the true function or the false function is executed. |
| 399 | * If no function exists for a particular branch then an empty |
| 400 | * Iterable is returned. |
| 401 | */ |
| 402 | private static class ConditionalDelegator<S,T> implements StepFunction<S,T>, Serializable |
| 403 | { |
| 404 | static final long serialVersionUID = 1L; |
| 405 | |
| 406 | private Predicate<? super S> condition; |
| 407 | private Function<S,? extends Iterable<T>> trueDelegate; |
| 408 | private Function<S,? extends Iterable<T>> falseDelegate; |
| 409 | |
| 410 | public ConditionalDelegator( Predicate<? super S> condition, |
| 411 | Function<S,? extends Iterable<T>> trueDelegate, |
| 412 | Function<S,? extends Iterable<T>> falseDelegate ) |
| 413 | { |
| 414 | this.condition = condition; |
| 415 | this.trueDelegate = trueDelegate; |
| 416 | this.falseDelegate = falseDelegate; |
| 417 | } |
| 418 | |
| 419 | public Iterable<T> apply( S object ) |
| 420 | { |
| 421 | if( condition == null || condition.apply(object) ) |
| 422 | { |
| 423 | if( trueDelegate != null ) |
| 424 | return trueDelegate.apply(object); |
| 425 | } |
| 426 | else |
| 427 | { |
| 428 | if( falseDelegate != null ) |
| 429 | return falseDelegate.apply(object); |
| 430 | } |
| 431 | return Collections.emptySet(); |
| 432 | } |
| 433 | |
| 434 | public String toString() |
| 435 | { |
| 436 | return "Branch[condition=" + condition |
| 437 | + ", true:" + trueDelegate |
| 438 | + ", false:" + falseDelegate + "]"; |
| 439 | } |
| 440 | } |
| 441 | |
| 442 | /** |
| 443 | * Step function that delegates to another function but |
| 444 | * wraps its result in a singleton collection to meet the |
| 445 | * StepFunction contract. |
| 446 | */ |
| 447 | private static class TransformDecorator<S,T> implements StepFunction<S,T>, Serializable |
| 448 | { |
| 449 | static final long serialVersionUID = 1L; |
| 450 | |
| 451 | private Function<S,T> transform; |
| 452 | |
| 453 | public TransformDecorator( Function<S,T> transform ) |
| 454 | { |
| 455 | if( transform == null ) |
| 456 | throw new IllegalArgumentException( "transform cannot be null." ); |
| 457 | this.transform = transform; |
| 458 | } |
| 459 | |
| 460 | public Iterable<T> apply( S object ) |
| 461 | { |
| 462 | T result = transform.apply( object ); |
| 463 | return Collections.singleton( result ); |
| 464 | } |
| 465 | |
| 466 | public String toString() |
| 467 | { |
| 468 | return "Transform[" + transform + "]"; |
| 469 | } |
| 470 | } |
| 471 | |
| 472 | private static class FilterDecorator<T> implements StepFunction<T,T>, Serializable |
| 473 | { |
| 474 | static final long serialVersionUID = 1L; |
| 475 | |
| 476 | private Predicate<T> filter; |
| 477 | |
| 478 | public FilterDecorator( Predicate<T> filter ) |
| 479 | { |
| 480 | if( filter == null ) |
| 481 | throw new IllegalArgumentException( "filter cannot be null." ); |
| 482 | this.filter = filter; |
| 483 | } |
| 484 | |
| 485 | public Iterable<T> apply( T object ) |
| 486 | { |
| 487 | if( !filter.apply(object) ) |
| 488 | return Collections.emptySet(); |
| 489 | return Collections.singleton( object ); |
| 490 | } |
| 491 | |
| 492 | public String toString() |
| 493 | { |
| 494 | return "Filter[" + filter + "]"; |
| 495 | } |
| 496 | } |
| 497 | |
| 498 | // Note to self: if you ever think you need a prefilter function, |
| 499 | // take a deep breath and go back and look at branch()/ConditionalDelegator. |
| 500 | // It's the uber-prefilter function. |
| 501 | private static class FilterFunction<S,T> implements StepFunction<S,T>, Serializable |
| 502 | { |
| 503 | static final long serialVersionUID = 1L; |
| 504 | |
| 505 | private Function<S,? extends Iterable<T>> delegate; |
| 506 | private Predicate<? super T> filter; |
| 507 | |
| 508 | public FilterFunction( Function<S,? extends Iterable<T>> delegate, Predicate<? super T> filter ) |
| 509 | { |
| 510 | if( delegate == null ) |
| 511 | throw new IllegalArgumentException( "delegate cannot be null." ); |
| 512 | if( filter == null ) |
| 513 | throw new IllegalArgumentException( "filter cannot be null." ); |
| 514 | this.delegate = delegate; |
| 515 | this.filter = filter; |
| 516 | } |
| 517 | |
| 518 | public Iterable<T> apply( S object ) |
| 519 | { |
| 520 | Iterable<T> results = delegate.apply(object); |
| 521 | return Iterables.filter( results, filter ); |
| 522 | } |
| 523 | |
| 524 | public String toString() |
| 525 | { |
| 526 | return "Filter[" + delegate + " : " + filter + "]"; |
| 527 | } |
| 528 | } |
| 529 | |
| 530 | private static class TransformFunction<A,B,C> implements StepFunction<A,C>, Serializable |
| 531 | { |
| 532 | static final long serialVersionUID = 1L; |
| 533 | |
| 534 | private Function<A,? extends Iterable<B>> delegate; |
| 535 | private Function<? super B,C> transform; |
| 536 | |
| 537 | public TransformFunction( Function<A,? extends Iterable<B>> delegate, |
| 538 | Function<? super B,C> transform ) |
| 539 | { |
| 540 | if( delegate == null ) |
| 541 | throw new IllegalArgumentException( "delegate cannot be null." ); |
| 542 | if( transform == null ) |
| 543 | throw new IllegalArgumentException( "transform cannot be null." ); |
| 544 | this.delegate = delegate; |
| 545 | this.transform = transform; |
| 546 | } |
| 547 | |
| 548 | public Iterable<C> apply( A object ) |
| 549 | { |
| 550 | Iterable<B> results = delegate.apply(object); |
| 551 | return Iterables.transform( results, transform ); |
| 552 | } |
| 553 | |
| 554 | public String toString() |
| 555 | { |
| 556 | return "Transform[" + delegate + " : " + transform + "]"; |
| 557 | } |
| 558 | } |
| 559 | |
| 560 | private static class ConcatFunction<S,T> implements StepFunction<S,T>, Serializable |
| 561 | { |
| 562 | static final long serialVersionUID = 1L; |
| 563 | |
| 564 | private Function<S,? extends Iterable<T>> f1; |
| 565 | private Function<S,? extends Iterable<T>> f2; |
| 566 | |
| 567 | public ConcatFunction( Function<S,? extends Iterable<T>> f1, |
| 568 | Function<S,? extends Iterable<T>> f2 ) |
| 569 | { |
| 570 | if( f1 == null || f2 == null ) |
| 571 | throw new IllegalArgumentException( "Supplied functions cannot be null." ); |
| 572 | this.f1 = f1; |
| 573 | this.f2 = f2; |
| 574 | } |
| 575 | |
| 576 | public Iterable<T> apply( S object ) |
| 577 | { |
| 578 | Iterable<T> r1 = f1.apply(object); |
| 579 | Iterable<T> r2 = f2.apply(object); |
| 580 | return Iterables.concat( r1, r2 ); |
| 581 | } |
| 582 | |
| 583 | public String toString() |
| 584 | { |
| 585 | return "Concat[" + f1 + " + " + f2 + "]"; |
| 586 | } |
| 587 | } |
| 588 | |
| 589 | } |