1 /* 2 * Hunt - A refined core library for D programming language. 3 * 4 * Copyright (C) 2018-2019 HuntLabs 5 * 6 * Website: https://www.huntlabs.net/ 7 * 8 * Licensed under the Apache-2.0 License. 9 * 10 */ 11 12 module hunt.collection.Deque; 13 14 15 import hunt.collection.Queue; 16 17 /** 18 * A linear collection that supports element insertion and removal at 19 * both ends. The name <i>deque</i> is short for "double ended queue" 20 * and is usually pronounced "deck". Most {@code Deque} 21 * implementations place no fixed limits on the number of elements 22 * they may contain, but this interface supports capacity-restricted 23 * deques as well as those with no fixed size limit. 24 * 25 * <p>This interface defines methods to access the elements at both 26 * ends of the deque. Methods are provided to insert, remove, and 27 * examine the element. Each of these methods exists in two forms: 28 * one throws an exception if the operation fails, the other returns a 29 * special value (either {@code null} or {@code false}, depending on 30 * the operation). The latter form of the insert operation is 31 * designed specifically for use with capacity-restricted 32 * {@code Deque} implementations; in most implementations, insert 33 * operations cannot fail. 34 * 35 * <p>The twelve methods described above are summarized in the 36 * following table: 37 * 38 * <table BORDER CELLPADDING=3 CELLSPACING=1> 39 * <caption>Summary of Deque methods</caption> 40 * <tr> 41 * <td></td> 42 * <td ALIGN=CENTER COLSPAN = 2> <b>First Element (Head)</b></td> 43 * <td ALIGN=CENTER COLSPAN = 2> <b>Last Element (Tail)</b></td> 44 * </tr> 45 * <tr> 46 * <td></td> 47 * <td ALIGN=CENTER><em>Throws exception</em></td> 48 * <td ALIGN=CENTER><em>Special value</em></td> 49 * <td ALIGN=CENTER><em>Throws exception</em></td> 50 * <td ALIGN=CENTER><em>Special value</em></td> 51 * </tr> 52 * <tr> 53 * <td><b>Insert</b></td> 54 * <td>{@link Deque#addFirst addFirst(e)}</td> 55 * <td>{@link Deque#offerFirst offerFirst(e)}</td> 56 * <td>{@link Deque#addLast addLast(e)}</td> 57 * <td>{@link Deque#offerLast offerLast(e)}</td> 58 * </tr> 59 * <tr> 60 * <td><b>Remove</b></td> 61 * <td>{@link Deque#removeFirst removeFirst()}</td> 62 * <td>{@link Deque#pollFirst pollFirst()}</td> 63 * <td>{@link Deque#removeLast removeLast()}</td> 64 * <td>{@link Deque#pollLast pollLast()}</td> 65 * </tr> 66 * <tr> 67 * <td><b>Examine</b></td> 68 * <td>{@link Deque#getFirst getFirst()}</td> 69 * <td>{@link Deque#peekFirst peekFirst()}</td> 70 * <td>{@link Deque#getLast getLast()}</td> 71 * <td>{@link Deque#peekLast peekLast()}</td> 72 * </tr> 73 * </table> 74 * 75 * <p>This interface extends the {@link Queue} interface. When a deque is 76 * used as a queue, FIFO (First-In-First-Out) behavior results. Elements are 77 * added at the end of the deque and removed from the beginning. The methods 78 * inherited from the {@code Queue} interface are precisely equivalent to 79 * {@code Deque} methods as indicated in the following table: 80 * 81 * <table BORDER CELLPADDING=3 CELLSPACING=1> 82 * <caption>Comparison of Queue and Deque methods</caption> 83 * <tr> 84 * <td ALIGN=CENTER> <b>{@code Queue} Method</b></td> 85 * <td ALIGN=CENTER> <b>Equivalent {@code Deque} Method</b></td> 86 * </tr> 87 * <tr> 88 * <td>{@link java.util.Queue#add add(e)}</td> 89 * <td>{@link #addLast addLast(e)}</td> 90 * </tr> 91 * <tr> 92 * <td>{@link java.util.Queue#offer offer(e)}</td> 93 * <td>{@link #offerLast offerLast(e)}</td> 94 * </tr> 95 * <tr> 96 * <td>{@link java.util.Queue#remove remove()}</td> 97 * <td>{@link #removeFirst removeFirst()}</td> 98 * </tr> 99 * <tr> 100 * <td>{@link java.util.Queue#poll poll()}</td> 101 * <td>{@link #pollFirst pollFirst()}</td> 102 * </tr> 103 * <tr> 104 * <td>{@link java.util.Queue#element element()}</td> 105 * <td>{@link #getFirst getFirst()}</td> 106 * </tr> 107 * <tr> 108 * <td>{@link java.util.Queue#peek peek()}</td> 109 * <td>{@link #peek peekFirst()}</td> 110 * </tr> 111 * </table> 112 * 113 * <p>Deques can also be used as LIFO (Last-In-First-Out) stacks. This 114 * interface should be used in preference to the legacy {@link Stack} class. 115 * When a deque is used as a stack, elements are pushed and popped from the 116 * beginning of the deque. Stack methods are precisely equivalent to 117 * {@code Deque} methods as indicated in the table below: 118 * 119 * <table BORDER CELLPADDING=3 CELLSPACING=1> 120 * <caption>Comparison of Stack and Deque methods</caption> 121 * <tr> 122 * <td ALIGN=CENTER> <b>Stack Method</b></td> 123 * <td ALIGN=CENTER> <b>Equivalent {@code Deque} Method</b></td> 124 * </tr> 125 * <tr> 126 * <td>{@link #push push(e)}</td> 127 * <td>{@link #addFirst addFirst(e)}</td> 128 * </tr> 129 * <tr> 130 * <td>{@link #pop pop()}</td> 131 * <td>{@link #removeFirst removeFirst()}</td> 132 * </tr> 133 * <tr> 134 * <td>{@link #peek peek()}</td> 135 * <td>{@link #peekFirst peekFirst()}</td> 136 * </tr> 137 * </table> 138 * 139 * <p>Note that the {@link #peek peek} method works equally well when 140 * a deque is used as a queue or a stack; in either case, elements are 141 * drawn from the beginning of the deque. 142 * 143 * <p>This interface provides two methods to remove interior 144 * elements, {@link #removeFirstOccurrence removeFirstOccurrence} and 145 * {@link #removeLastOccurrence removeLastOccurrence}. 146 * 147 * <p>Unlike the {@link List} interface, this interface does not 148 * provide support for indexed access to elements. 149 * 150 * <p>While {@code Deque} implementations are not strictly required 151 * to prohibit the insertion of null elements, they are strongly 152 * encouraged to do so. Users of any {@code Deque} implementations 153 * that do allow null elements are strongly encouraged <i>not</i> to 154 * take advantage of the ability to insert nulls. This is so because 155 * {@code null} is used as a special return value by various methods 156 * to indicated that the deque is empty. 157 * 158 * <p>{@code Deque} implementations generally do not define 159 * element-based versions of the {@code equals} and {@code hashCode} 160 * methods, but instead inherit the identity-based versions from class 161 * {@code Object}. 162 * 163 * <p>This interface is a member of the <a 164 * href="{@docRoot}/../technotes/guides/collections/index.html"> Java Collections 165 * Framework</a>. 166 * 167 * @author Doug Lea 168 * @author Josh Bloch 169 * @since 1.6 170 * @param !E the type of elements held in this collection 171 */ 172 interface Deque(E) : Queue!E { 173 /** 174 * Inserts the specified element at the front of this deque if it is 175 * possible to do so immediately without violating capacity restrictions, 176 * throwing an {@code IllegalStateException} if no space is currently 177 * available. When using a capacity-restricted deque, it is generally 178 * preferable to use method {@link #offerFirst}. 179 * 180 * @param e the element to add 181 * @throws IllegalStateException if the element cannot be added at this 182 * time due to capacity restrictions 183 * @throws ClassCastException if the class of the specified element 184 * prevents it from being added to this deque 185 * @throws NullPointerException if the specified element is null and this 186 * deque does not permit null elements 187 * @throws IllegalArgumentException if some property of the specified 188 * element prevents it from being added to this deque 189 */ 190 void addFirst(E e); 191 192 /** 193 * Inserts the specified element at the end of this deque if it is 194 * possible to do so immediately without violating capacity restrictions, 195 * throwing an {@code IllegalStateException} if no space is currently 196 * available. When using a capacity-restricted deque, it is generally 197 * preferable to use method {@link #offerLast}. 198 * 199 * <p>This method is equivalent to {@link #add}. 200 * 201 * @param e the element to add 202 * @throws IllegalStateException if the element cannot be added at this 203 * time due to capacity restrictions 204 * @throws ClassCastException if the class of the specified element 205 * prevents it from being added to this deque 206 * @throws NullPointerException if the specified element is null and this 207 * deque does not permit null elements 208 * @throws IllegalArgumentException if some property of the specified 209 * element prevents it from being added to this deque 210 */ 211 void addLast(E e); 212 213 /** 214 * Inserts the specified element at the front of this deque unless it would 215 * violate capacity restrictions. When using a capacity-restricted deque, 216 * this method is generally preferable to the {@link #addFirst} method, 217 * which can fail to insert an element only by throwing an exception. 218 * 219 * @param e the element to add 220 * @return {@code true} if the element was added to this deque, else 221 * {@code false} 222 * @throws ClassCastException if the class of the specified element 223 * prevents it from being added to this deque 224 * @throws NullPointerException if the specified element is null and this 225 * deque does not permit null elements 226 * @throws IllegalArgumentException if some property of the specified 227 * element prevents it from being added to this deque 228 */ 229 bool offerFirst(E e); 230 231 /** 232 * Inserts the specified element at the end of this deque unless it would 233 * violate capacity restrictions. When using a capacity-restricted deque, 234 * this method is generally preferable to the {@link #addLast} method, 235 * which can fail to insert an element only by throwing an exception. 236 * 237 * @param e the element to add 238 * @return {@code true} if the element was added to this deque, else 239 * {@code false} 240 * @throws ClassCastException if the class of the specified element 241 * prevents it from being added to this deque 242 * @throws NullPointerException if the specified element is null and this 243 * deque does not permit null elements 244 * @throws IllegalArgumentException if some property of the specified 245 * element prevents it from being added to this deque 246 */ 247 bool offerLast(E e); 248 249 /** 250 * Retrieves and removes the first element of this deque. This method 251 * differs from {@link #pollFirst pollFirst} only in that it throws an 252 * exception if this deque is empty. 253 * 254 * @return the head of this deque 255 * @throws NoSuchElementException if this deque is empty 256 */ 257 E removeFirst(); 258 259 /** 260 * Retrieves and removes the last element of this deque. This method 261 * differs from {@link #pollLast pollLast} only in that it throws an 262 * exception if this deque is empty. 263 * 264 * @return the tail of this deque 265 * @throws NoSuchElementException if this deque is empty 266 */ 267 E removeLast(); 268 269 /** 270 * Retrieves and removes the first element of this deque, 271 * or returns {@code null} if this deque is empty. 272 * 273 * @return the head of this deque, or {@code null} if this deque is empty 274 */ 275 E pollFirst(); 276 277 /** 278 * Retrieves and removes the last element of this deque, 279 * or returns {@code null} if this deque is empty. 280 * 281 * @return the tail of this deque, or {@code null} if this deque is empty 282 */ 283 E pollLast(); 284 285 /** 286 * Retrieves, but does not remove, the first element of this deque. 287 * 288 * This method differs from {@link #peekFirst peekFirst} only in that it 289 * throws an exception if this deque is empty. 290 * 291 * @return the head of this deque 292 * @throws NoSuchElementException if this deque is empty 293 */ 294 E getFirst(); 295 296 /** 297 * Retrieves, but does not remove, the last element of this deque. 298 * This method differs from {@link #peekLast peekLast} only in that it 299 * throws an exception if this deque is empty. 300 * 301 * @return the tail of this deque 302 * @throws NoSuchElementException if this deque is empty 303 */ 304 E getLast(); 305 306 /** 307 * Retrieves, but does not remove, the first element of this deque, 308 * or returns {@code null} if this deque is empty. 309 * 310 * @return the head of this deque, or {@code null} if this deque is empty 311 */ 312 E peekFirst(); 313 314 /** 315 * Retrieves, but does not remove, the last element of this deque, 316 * or returns {@code null} if this deque is empty. 317 * 318 * @return the tail of this deque, or {@code null} if this deque is empty 319 */ 320 E peekLast(); 321 322 /** 323 * Removes the first occurrence of the specified element from this deque. 324 * If the deque does not contain the element, it is unchanged. 325 * More formally, removes the first element {@code e} such that 326 * <tt>(o==null ? e==null : o.equals(e))</tt> 327 * (if such an element exists). 328 * Returns {@code true} if this deque contained the specified element 329 * (or equivalently, if this deque changed as a result of the call). 330 * 331 * @param o element to be removed from this deque, if present 332 * @return {@code true} if an element was removed as a result of this call 333 * @throws ClassCastException if the class of the specified element 334 * is incompatible with this deque 335 * (<a href="Collection.html#optional-restrictions">optional</a>) 336 * @throws NullPointerException if the specified element is null and this 337 * deque does not permit null elements 338 * (<a href="Collection.html#optional-restrictions">optional</a>) 339 */ 340 bool removeFirstOccurrence(E o); 341 342 /** 343 * Removes the last occurrence of the specified element from this deque. 344 * If the deque does not contain the element, it is unchanged. 345 * More formally, removes the last element {@code e} such that 346 * <tt>(o==null ? e==null : o.equals(e))</tt> 347 * (if such an element exists). 348 * Returns {@code true} if this deque contained the specified element 349 * (or equivalently, if this deque changed as a result of the call). 350 * 351 * @param o element to be removed from this deque, if present 352 * @return {@code true} if an element was removed as a result of this call 353 * @throws ClassCastException if the class of the specified element 354 * is incompatible with this deque 355 * (<a href="Collection.html#optional-restrictions">optional</a>) 356 * @throws NullPointerException if the specified element is null and this 357 * deque does not permit null elements 358 * (<a href="Collection.html#optional-restrictions">optional</a>) 359 */ 360 // bool removeLastOccurrence(E o); 361 362 // *** Queue methods *** 363 364 /** 365 * Inserts the specified element into the queue represented by this deque 366 * (in other words, at the tail of this deque) if it is possible to do so 367 * immediately without violating capacity restrictions, returning 368 * {@code true} upon success and throwing an 369 * {@code IllegalStateException} if no space is currently available. 370 * When using a capacity-restricted deque, it is generally preferable to 371 * use {@link #offer(Object) offer}. 372 * 373 * <p>This method is equivalent to {@link #addLast}. 374 * 375 * @param e the element to add 376 * @return {@code true} (as specified by {@link Collection#add}) 377 * @throws IllegalStateException if the element cannot be added at this 378 * time due to capacity restrictions 379 * @throws ClassCastException if the class of the specified element 380 * prevents it from being added to this deque 381 * @throws NullPointerException if the specified element is null and this 382 * deque does not permit null elements 383 * @throws IllegalArgumentException if some property of the specified 384 * element prevents it from being added to this deque 385 */ 386 bool add(E e); 387 388 /** 389 * Inserts the specified element into the queue represented by this deque 390 * (in other words, at the tail of this deque) if it is possible to do so 391 * immediately without violating capacity restrictions, returning 392 * {@code true} upon success and {@code false} if no space is currently 393 * available. When using a capacity-restricted deque, this method is 394 * generally preferable to the {@link #add} method, which can fail to 395 * insert an element only by throwing an exception. 396 * 397 * <p>This method is equivalent to {@link #offerLast}. 398 * 399 * @param e the element to add 400 * @return {@code true} if the element was added to this deque, else 401 * {@code false} 402 * @throws ClassCastException if the class of the specified element 403 * prevents it from being added to this deque 404 * @throws NullPointerException if the specified element is null and this 405 * deque does not permit null elements 406 * @throws IllegalArgumentException if some property of the specified 407 * element prevents it from being added to this deque 408 */ 409 bool offer(E e); 410 411 /** 412 * Retrieves and removes the head of the queue represented by this deque 413 * (in other words, the first element of this deque). 414 * This method differs from {@link #poll poll} only in that it throws an 415 * exception if this deque is empty. 416 * 417 * <p>This method is equivalent to {@link #removeFirst()}. 418 * 419 * @return the head of the queue represented by this deque 420 * @throws NoSuchElementException if this deque is empty 421 */ 422 E remove(); 423 424 /** 425 * Retrieves and removes the head of the queue represented by this deque 426 * (in other words, the first element of this deque), or returns 427 * {@code null} if this deque is empty. 428 * 429 * <p>This method is equivalent to {@link #pollFirst()}. 430 * 431 * @return the first element of this deque, or {@code null} if 432 * this deque is empty 433 */ 434 E poll(); 435 436 /** 437 * Retrieves, but does not remove, the head of the queue represented by 438 * this deque (in other words, the first element of this deque). 439 * This method differs from {@link #peek peek} only in that it throws an 440 * exception if this deque is empty. 441 * 442 * <p>This method is equivalent to {@link #getFirst()}. 443 * 444 * @return the head of the queue represented by this deque 445 * @throws NoSuchElementException if this deque is empty 446 */ 447 E element(); 448 449 /** 450 * Retrieves, but does not remove, the head of the queue represented by 451 * this deque (in other words, the first element of this deque), or 452 * returns {@code null} if this deque is empty. 453 * 454 * <p>This method is equivalent to {@link #peekFirst()}. 455 * 456 * @return the head of the queue represented by this deque, or 457 * {@code null} if this deque is empty 458 */ 459 E peek(); 460 461 462 // *** Stack methods *** 463 464 /** 465 * Pushes an element onto the stack represented by this deque (in other 466 * words, at the head of this deque) if it is possible to do so 467 * immediately without violating capacity restrictions, throwing an 468 * {@code IllegalStateException} if no space is currently available. 469 * 470 * <p>This method is equivalent to {@link #addFirst}. 471 * 472 * @param e the element to push 473 * @throws IllegalStateException if the element cannot be added at this 474 * time due to capacity restrictions 475 * @throws ClassCastException if the class of the specified element 476 * prevents it from being added to this deque 477 * @throws NullPointerException if the specified element is null and this 478 * deque does not permit null elements 479 * @throws IllegalArgumentException if some property of the specified 480 * element prevents it from being added to this deque 481 */ 482 void push(E e); 483 484 /** 485 * Pops an element from the stack represented by this deque. In other 486 * words, removes and returns the first element of this deque. 487 * 488 * <p>This method is equivalent to {@link #removeFirst()}. 489 * 490 * @return the element at the front of this deque (which is the top 491 * of the stack represented by this deque) 492 * @throws NoSuchElementException if this deque is empty 493 */ 494 E pop(); 495 496 497 // *** Collection methods *** 498 499 /** 500 * Removes the first occurrence of the specified element from this deque. 501 * If the deque does not contain the element, it is unchanged. 502 * More formally, removes the first element {@code e} such that 503 * <tt>(o==null ? e==null : o.equals(e))</tt> 504 * (if such an element exists). 505 * Returns {@code true} if this deque contained the specified element 506 * (or equivalently, if this deque changed as a result of the call). 507 * 508 * <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}. 509 * 510 * @param o element to be removed from this deque, if present 511 * @return {@code true} if an element was removed as a result of this call 512 * @throws ClassCastException if the class of the specified element 513 * is incompatible with this deque 514 * (<a href="Collection.html#optional-restrictions">optional</a>) 515 * @throws NullPointerException if the specified element is null and this 516 * deque does not permit null elements 517 * (<a href="Collection.html#optional-restrictions">optional</a>) 518 */ 519 bool remove(E o); 520 521 /** 522 * Returns {@code true} if this deque contains the specified element. 523 * More formally, returns {@code true} if and only if this deque contains 524 * at least one element {@code e} such that 525 * <tt>(o==null ? e==null : o.equals(e))</tt>. 526 * 527 * @param o element whose presence in this deque is to be tested 528 * @return {@code true} if this deque contains the specified element 529 * @throws ClassCastException if the type of the specified element 530 * is incompatible with this deque 531 * (<a href="Collection.html#optional-restrictions">optional</a>) 532 * @throws NullPointerException if the specified element is null and this 533 * deque does not permit null elements 534 * (<a href="Collection.html#optional-restrictions">optional</a>) 535 */ 536 bool contains(E o); 537 538 /** 539 * Returns the number of elements in this deque. 540 * 541 * @return the number of elements in this deque 542 */ 543 int size(); 544 545 /** 546 * Returns an iterator over the elements in this deque in proper sequence. 547 * The elements will be returned in order from first (head) to last (tail). 548 * 549 * @return an iterator over the elements in this deque in proper sequence 550 */ 551 // Iterator!E iterator(); 552 553 /** 554 * Returns an iterator over the elements in this deque in reverse 555 * sequential order. The elements will be returned in order from 556 * last (tail) to first (head). 557 * 558 * @return an iterator over the elements in this deque in reverse 559 * sequence 560 */ 561 // Iterator!E descendingIterator(); 562 563 }