jit: document union types
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1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT LIBRARY COMPONENTS --
4 -- --
5 -- A D A . C O N T A I N E R S . H A S H E D _ S E T S --
6 -- --
7 -- S p e c --
8 -- --
9 -- Copyright (C) 2004-2015, Free Software Foundation, Inc. --
10 -- --
11 -- This specification is derived from the Ada Reference Manual for use with --
12 -- GNAT. The copyright notice above, and the license provisions that follow --
13 -- apply solely to the contents of the part following the private keyword. --
14 -- --
15 -- GNAT is free software; you can redistribute it and/or modify it under --
16 -- terms of the GNU General Public License as published by the Free Soft- --
17 -- ware Foundation; either version 3, or (at your option) any later ver- --
18 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
19 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
20 -- or FITNESS FOR A PARTICULAR PURPOSE. --
21 -- --
22 -- As a special exception under Section 7 of GPL version 3, you are granted --
23 -- additional permissions described in the GCC Runtime Library Exception, --
24 -- version 3.1, as published by the Free Software Foundation. --
25 -- --
26 -- You should have received a copy of the GNU General Public License and --
27 -- a copy of the GCC Runtime Library Exception along with this program; --
28 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
29 -- <http://www.gnu.org/licenses/>. --
30 -- --
31 -- This unit was originally developed by Matthew J Heaney. --
32 ------------------------------------------------------------------------------
34 with Ada.Iterator_Interfaces;
36 private with Ada.Containers.Hash_Tables;
37 private with Ada.Finalization;
38 private with Ada.Streams;
40 generic
41 type Element_Type is private;
43 with function Hash (Element : Element_Type) return Hash_Type;
45 with function Equivalent_Elements
46 (Left, Right : Element_Type) return Boolean;
48 with function "=" (Left, Right : Element_Type) return Boolean is <>;
50 package Ada.Containers.Hashed_Sets is
51 pragma Preelaborate;
52 pragma Remote_Types;
54 type Set is tagged private
55 with
56 Constant_Indexing => Constant_Reference,
57 Default_Iterator => Iterate,
58 Iterator_Element => Element_Type;
60 pragma Preelaborable_Initialization (Set);
62 type Cursor is private;
63 pragma Preelaborable_Initialization (Cursor);
65 Empty_Set : constant Set;
66 -- Set objects declared without an initialization expression are
67 -- initialized to the value Empty_Set.
69 No_Element : constant Cursor;
70 -- Cursor objects declared without an initialization expression are
71 -- initialized to the value No_Element.
73 function Has_Element (Position : Cursor) return Boolean;
74 -- Equivalent to Position /= No_Element
76 package Set_Iterator_Interfaces is new
77 Ada.Iterator_Interfaces (Cursor, Has_Element);
79 function "=" (Left, Right : Set) return Boolean;
80 -- For each element in Left, set equality attempts to find the equal
81 -- element in Right; if a search fails, then set equality immediately
82 -- returns False. The search works by calling Hash to find the bucket in
83 -- the Right set that corresponds to the Left element. If the bucket is
84 -- non-empty, the search calls the generic formal element equality operator
85 -- to compare the element (in Left) to the element of each node in the
86 -- bucket (in Right); the search terminates when a matching node in the
87 -- bucket is found, or the nodes in the bucket are exhausted. (Note that
88 -- element equality is called here, not Equivalent_Elements. Set equality
89 -- is the only operation in which element equality is used. Compare set
90 -- equality to Equivalent_Sets, which does call Equivalent_Elements.)
92 function Equivalent_Sets (Left, Right : Set) return Boolean;
93 -- Similar to set equality, with the difference that the element in Left is
94 -- compared to the elements in Right using the generic formal
95 -- Equivalent_Elements operation instead of element equality.
97 function To_Set (New_Item : Element_Type) return Set;
98 -- Constructs a singleton set comprising New_Element. To_Set calls Hash to
99 -- determine the bucket for New_Item.
101 function Capacity (Container : Set) return Count_Type;
102 -- Returns the current capacity of the set. Capacity is the maximum length
103 -- before which rehashing in guaranteed not to occur.
105 procedure Reserve_Capacity (Container : in out Set; Capacity : Count_Type);
106 -- Adjusts the current capacity, by allocating a new buckets array. If the
107 -- requested capacity is less than the current capacity, then the capacity
108 -- is contracted (to a value not less than the current length). If the
109 -- requested capacity is greater than the current capacity, then the
110 -- capacity is expanded (to a value not less than what is requested). In
111 -- either case, the nodes are rehashed from the old buckets array onto the
112 -- new buckets array (Hash is called once for each existing element in
113 -- order to compute the new index), and then the old buckets array is
114 -- deallocated.
116 function Length (Container : Set) return Count_Type;
117 -- Returns the number of items in the set
119 function Is_Empty (Container : Set) return Boolean;
120 -- Equivalent to Length (Container) = 0
122 procedure Clear (Container : in out Set);
123 -- Removes all of the items from the set
125 function Element (Position : Cursor) return Element_Type;
126 -- Returns the element of the node designated by the cursor
128 procedure Replace_Element
129 (Container : in out Set;
130 Position : Cursor;
131 New_Item : Element_Type);
132 -- If New_Item is equivalent (as determined by calling Equivalent_Elements)
133 -- to the element of the node designated by Position, then New_Element is
134 -- assigned to that element. Otherwise, it calls Hash to determine the
135 -- bucket for New_Item. If the bucket is not empty, then it calls
136 -- Equivalent_Elements for each node in that bucket to determine whether
137 -- New_Item is equivalent to an element in that bucket. If
138 -- Equivalent_Elements returns True then Program_Error is raised (because
139 -- an element may appear only once in the set); otherwise, New_Item is
140 -- assigned to the node designated by Position, and the node is moved to
141 -- its new bucket.
143 procedure Query_Element
144 (Position : Cursor;
145 Process : not null access procedure (Element : Element_Type));
146 -- Calls Process with the element (having only a constant view) of the node
147 -- designed by the cursor.
149 type Constant_Reference_Type
150 (Element : not null access constant Element_Type) is private
151 with Implicit_Dereference => Element;
153 function Constant_Reference
154 (Container : aliased Set;
155 Position : Cursor) return Constant_Reference_Type;
156 pragma Inline (Constant_Reference);
158 procedure Assign (Target : in out Set; Source : Set);
160 function Copy (Source : Set; Capacity : Count_Type := 0) return Set;
162 procedure Move (Target : in out Set; Source : in out Set);
163 -- Clears Target (if it's not empty), and then moves (not copies) the
164 -- buckets array and nodes from Source to Target.
166 procedure Insert
167 (Container : in out Set;
168 New_Item : Element_Type;
169 Position : out Cursor;
170 Inserted : out Boolean);
171 -- Conditionally inserts New_Item into the set. If New_Item is already in
172 -- the set, then Inserted returns False and Position designates the node
173 -- containing the existing element (which is not modified). If New_Item is
174 -- not already in the set, then Inserted returns True and Position
175 -- designates the newly-inserted node containing New_Item. The search for
176 -- an existing element works as follows. Hash is called to determine
177 -- New_Item's bucket; if the bucket is non-empty, then Equivalent_Elements
178 -- is called to compare New_Item to the element of each node in that
179 -- bucket. If the bucket is empty, or there were no equivalent elements in
180 -- the bucket, the search "fails" and the New_Item is inserted in the set
181 -- (and Inserted returns True); otherwise, the search "succeeds" (and
182 -- Inserted returns False).
184 procedure Insert (Container : in out Set; New_Item : Element_Type);
185 -- Attempts to insert New_Item into the set, performing the usual insertion
186 -- search (which involves calling both Hash and Equivalent_Elements); if
187 -- the search succeeds (New_Item is equivalent to an element already in the
188 -- set, and so was not inserted), then this operation raises
189 -- Constraint_Error. (This version of Insert is similar to Replace, but
190 -- having the opposite exception behavior. It is intended for use when you
191 -- want to assert that the item is not already in the set.)
193 procedure Include (Container : in out Set; New_Item : Element_Type);
194 -- Attempts to insert New_Item into the set. If an element equivalent to
195 -- New_Item is already in the set (the insertion search succeeded, and
196 -- hence New_Item was not inserted), then the value of New_Item is assigned
197 -- to the existing element. (This insertion operation only raises an
198 -- exception if cursor tampering occurs. It is intended for use when you
199 -- want to insert the item in the set, and you don't care whether an
200 -- equivalent element is already present.)
202 procedure Replace (Container : in out Set; New_Item : Element_Type);
203 -- Searches for New_Item in the set; if the search fails (because an
204 -- equivalent element was not in the set), then it raises
205 -- Constraint_Error. Otherwise, the existing element is assigned the value
206 -- New_Item. (This is similar to Insert, but with the opposite exception
207 -- behavior. It is intended for use when you want to assert that the item
208 -- is already in the set.)
210 procedure Exclude (Container : in out Set; Item : Element_Type);
211 -- Searches for Item in the set, and if found, removes its node from the
212 -- set and then deallocates it. The search works as follows. The operation
213 -- calls Hash to determine the item's bucket; if the bucket is not empty,
214 -- it calls Equivalent_Elements to compare Item to the element of each node
215 -- in the bucket. (This is the deletion analog of Include. It is intended
216 -- for use when you want to remove the item from the set, but don't care
217 -- whether the item is already in the set.)
219 procedure Delete (Container : in out Set; Item : Element_Type);
220 -- Searches for Item in the set (which involves calling both Hash and
221 -- Equivalent_Elements). If the search fails, then the operation raises
222 -- Constraint_Error. Otherwise it removes the node from the set and then
223 -- deallocates it. (This is the deletion analog of non-conditional
224 -- Insert. It is intended for use when you want to assert that the item is
225 -- already in the set.)
227 procedure Delete (Container : in out Set; Position : in out Cursor);
228 -- Removes the node designated by Position from the set, and then
229 -- deallocates the node. The operation calls Hash to determine the bucket,
230 -- and then compares Position to each node in the bucket until there's a
231 -- match (it does not call Equivalent_Elements).
233 procedure Union (Target : in out Set; Source : Set);
234 -- The operation first calls Reserve_Capacity if the current capacity is
235 -- less than the sum of the lengths of Source and Target. It then iterates
236 -- over the Source set, and conditionally inserts each element into Target.
238 function Union (Left, Right : Set) return Set;
239 -- The operation first copies the Left set to the result, and then iterates
240 -- over the Right set to conditionally insert each element into the result.
242 function "or" (Left, Right : Set) return Set renames Union;
244 procedure Intersection (Target : in out Set; Source : Set);
245 -- Iterates over the Target set (calling First and Next), calling Find to
246 -- determine whether the element is in Source. If an equivalent element is
247 -- not found in Source, the element is deleted from Target.
249 function Intersection (Left, Right : Set) return Set;
250 -- Iterates over the Left set, calling Find to determine whether the
251 -- element is in Right. If an equivalent element is found, it is inserted
252 -- into the result set.
254 function "and" (Left, Right : Set) return Set renames Intersection;
256 procedure Difference (Target : in out Set; Source : Set);
257 -- Iterates over the Source (calling First and Next), calling Find to
258 -- determine whether the element is in Target. If an equivalent element is
259 -- found, it is deleted from Target.
261 function Difference (Left, Right : Set) return Set;
262 -- Iterates over the Left set, calling Find to determine whether the
263 -- element is in the Right set. If an equivalent element is not found, the
264 -- element is inserted into the result set.
266 function "-" (Left, Right : Set) return Set renames Difference;
268 procedure Symmetric_Difference (Target : in out Set; Source : Set);
269 -- The operation first calls Reserve_Capacity if the current capacity is
270 -- less than the sum of the lengths of Source and Target. It then iterates
271 -- over the Source set, searching for the element in Target (calling Hash
272 -- and Equivalent_Elements). If an equivalent element is found, it is
273 -- removed from Target; otherwise it is inserted into Target.
275 function Symmetric_Difference (Left, Right : Set) return Set;
276 -- The operation first iterates over the Left set. It calls Find to
277 -- determine whether the element is in the Right set. If no equivalent
278 -- element is found, the element from Left is inserted into the result. The
279 -- operation then iterates over the Right set, to determine whether the
280 -- element is in the Left set. If no equivalent element is found, the Right
281 -- element is inserted into the result.
283 function "xor" (Left, Right : Set) return Set
284 renames Symmetric_Difference;
286 function Overlap (Left, Right : Set) return Boolean;
287 -- Iterates over the Left set (calling First and Next), calling Find to
288 -- determine whether the element is in the Right set. If an equivalent
289 -- element is found, the operation immediately returns True. The operation
290 -- returns False if the iteration over Left terminates without finding any
291 -- equivalent element in Right.
293 function Is_Subset (Subset : Set; Of_Set : Set) return Boolean;
294 -- Iterates over Subset (calling First and Next), calling Find to determine
295 -- whether the element is in Of_Set. If no equivalent element is found in
296 -- Of_Set, the operation immediately returns False. The operation returns
297 -- True if the iteration over Subset terminates without finding an element
298 -- not in Of_Set (that is, every element in Subset is equivalent to an
299 -- element in Of_Set).
301 function First (Container : Set) return Cursor;
302 -- Returns a cursor that designates the first non-empty bucket, by
303 -- searching from the beginning of the buckets array.
305 function Next (Position : Cursor) return Cursor;
306 -- Returns a cursor that designates the node that follows the current one
307 -- designated by Position. If Position designates the last node in its
308 -- bucket, the operation calls Hash to compute the index of this bucket,
309 -- and searches the buckets array for the first non-empty bucket, starting
310 -- from that index; otherwise, it simply follows the link to the next node
311 -- in the same bucket.
313 procedure Next (Position : in out Cursor);
314 -- Equivalent to Position := Next (Position)
316 function Find
317 (Container : Set;
318 Item : Element_Type) return Cursor;
319 -- Searches for Item in the set. Find calls Hash to determine the item's
320 -- bucket; if the bucket is not empty, it calls Equivalent_Elements to
321 -- compare Item to each element in the bucket. If the search succeeds, Find
322 -- returns a cursor designating the node containing the equivalent element;
323 -- otherwise, it returns No_Element.
325 function Contains (Container : Set; Item : Element_Type) return Boolean;
326 -- Equivalent to Find (Container, Item) /= No_Element
328 function Equivalent_Elements (Left, Right : Cursor) return Boolean;
329 -- Returns the result of calling Equivalent_Elements with the elements of
330 -- the nodes designated by cursors Left and Right.
332 function Equivalent_Elements
333 (Left : Cursor;
334 Right : Element_Type) return Boolean;
335 -- Returns the result of calling Equivalent_Elements with element of the
336 -- node designated by Left and element Right.
338 function Equivalent_Elements
339 (Left : Element_Type;
340 Right : Cursor) return Boolean;
341 -- Returns the result of calling Equivalent_Elements with element Left and
342 -- the element of the node designated by Right.
344 procedure Iterate
345 (Container : Set;
346 Process : not null access procedure (Position : Cursor));
347 -- Calls Process for each node in the set
349 function Iterate
350 (Container : Set) return Set_Iterator_Interfaces.Forward_Iterator'Class;
352 generic
353 type Key_Type (<>) is private;
355 with function Key (Element : Element_Type) return Key_Type;
357 with function Hash (Key : Key_Type) return Hash_Type;
359 with function Equivalent_Keys (Left, Right : Key_Type) return Boolean;
361 package Generic_Keys is
363 function Key (Position : Cursor) return Key_Type;
364 -- Applies generic formal operation Key to the element of the node
365 -- designated by Position.
367 function Element (Container : Set; Key : Key_Type) return Element_Type;
368 -- Searches (as per the key-based Find) for the node containing Key, and
369 -- returns the associated element.
371 procedure Replace
372 (Container : in out Set;
373 Key : Key_Type;
374 New_Item : Element_Type);
375 -- Searches (as per the key-based Find) for the node containing Key, and
376 -- then replaces the element of that node (as per the element-based
377 -- Replace_Element).
379 procedure Exclude (Container : in out Set; Key : Key_Type);
380 -- Searches for Key in the set, and if found, removes its node from the
381 -- set and then deallocates it. The search works by first calling Hash
382 -- (on Key) to determine the bucket; if the bucket is not empty, it
383 -- calls Equivalent_Keys to compare parameter Key to the value of
384 -- generic formal operation Key applied to element of each node in the
385 -- bucket.
387 procedure Delete (Container : in out Set; Key : Key_Type);
388 -- Deletes the node containing Key as per Exclude, with the difference
389 -- that Constraint_Error is raised if Key is not found.
391 function Find (Container : Set; Key : Key_Type) return Cursor;
392 -- Searches for the node containing Key, and returns a cursor
393 -- designating the node. The search works by first calling Hash (on Key)
394 -- to determine the bucket. If the bucket is not empty, the search
395 -- compares Key to the element of each node in the bucket, and returns
396 -- the matching node. The comparison itself works by applying the
397 -- generic formal Key operation to the element of the node, and then
398 -- calling generic formal operation Equivalent_Keys.
400 function Contains (Container : Set; Key : Key_Type) return Boolean;
401 -- Equivalent to Find (Container, Key) /= No_Element
403 procedure Update_Element_Preserving_Key
404 (Container : in out Set;
405 Position : Cursor;
406 Process : not null access
407 procedure (Element : in out Element_Type));
408 -- Calls Process with the element of the node designated by Position,
409 -- but with the restriction that the key-value of the element is not
410 -- modified. The operation first makes a copy of the value returned by
411 -- applying generic formal operation Key on the element of the node, and
412 -- then calls Process with the element. The operation verifies that the
413 -- key-part has not been modified by calling generic formal operation
414 -- Equivalent_Keys to compare the saved key-value to the value returned
415 -- by applying generic formal operation Key to the post-Process value of
416 -- element. If the key values compare equal then the operation
417 -- completes. Otherwise, the node is removed from the set and
418 -- Program_Error is raised.
420 type Reference_Type (Element : not null access Element_Type) is private
421 with Implicit_Dereference => Element;
423 function Reference_Preserving_Key
424 (Container : aliased in out Set;
425 Position : Cursor) return Reference_Type;
427 function Constant_Reference
428 (Container : aliased Set;
429 Key : Key_Type) return Constant_Reference_Type;
431 function Reference_Preserving_Key
432 (Container : aliased in out Set;
433 Key : Key_Type) return Reference_Type;
435 private
436 use Ada.Streams;
437 type Set_Access is access all Set;
438 for Set_Access'Storage_Size use 0;
440 -- Key_Preserving references must carry information to allow removal
441 -- of elements whose value may have been altered improperly, i.e. have
442 -- been given values incompatible with the hash-code of the previous
443 -- value, and are thus in the wrong bucket. (RM 18.7 (96.6/3))
445 -- We cannot store the key directly because it is an unconstrained type.
446 -- To avoid using additional dynamic allocation we store the old cursor
447 -- which simplifies possible removal. This is not possible for some
448 -- other set types.
450 -- The mechanism is different for Update_Element_Preserving_Key, as
451 -- in that case the check that buckets have not changed is performed
452 -- at the time of the update, not when the reference is finalized.
454 type Reference_Control_Type is
455 new Ada.Finalization.Controlled with
456 record
457 Container : Set_Access;
458 Index : Hash_Type;
459 Old_Pos : Cursor;
460 Old_Hash : Hash_Type;
461 end record;
463 overriding procedure Adjust (Control : in out Reference_Control_Type);
464 pragma Inline (Adjust);
466 overriding procedure Finalize (Control : in out Reference_Control_Type);
467 pragma Inline (Finalize);
469 type Reference_Type (Element : not null access Element_Type) is record
470 Control : Reference_Control_Type;
471 end record;
473 procedure Read
474 (Stream : not null access Root_Stream_Type'Class;
475 Item : out Reference_Type);
477 for Reference_Type'Read use Read;
479 procedure Write
480 (Stream : not null access Root_Stream_Type'Class;
481 Item : Reference_Type);
483 for Reference_Type'Write use Write;
484 end Generic_Keys;
486 private
487 pragma Inline (Next);
489 type Node_Type;
490 type Node_Access is access Node_Type;
492 type Node_Type is limited record
493 Element : aliased Element_Type;
494 Next : Node_Access;
495 end record;
497 package HT_Types is
498 new Hash_Tables.Generic_Hash_Table_Types (Node_Type, Node_Access);
500 type Set is new Ada.Finalization.Controlled with record
501 HT : HT_Types.Hash_Table_Type;
502 end record;
504 overriding procedure Adjust (Container : in out Set);
506 overriding procedure Finalize (Container : in out Set);
508 use HT_Types;
509 use Ada.Finalization;
510 use Ada.Streams;
512 procedure Write
513 (Stream : not null access Root_Stream_Type'Class;
514 Container : Set);
516 for Set'Write use Write;
518 procedure Read
519 (Stream : not null access Root_Stream_Type'Class;
520 Container : out Set);
522 for Set'Read use Read;
524 type Set_Access is access all Set;
525 for Set_Access'Storage_Size use 0;
527 type Cursor is record
528 Container : Set_Access;
529 Node : Node_Access;
530 end record;
532 type Reference_Control_Type is new Ada.Finalization.Controlled with record
533 Container : Set_Access;
534 end record;
536 procedure Write
537 (Stream : not null access Root_Stream_Type'Class;
538 Item : Cursor);
540 for Cursor'Write use Write;
542 procedure Read
543 (Stream : not null access Root_Stream_Type'Class;
544 Item : out Cursor);
546 for Cursor'Read use Read;
548 overriding procedure Adjust (Control : in out Reference_Control_Type);
549 pragma Inline (Adjust);
551 overriding procedure Finalize (Control : in out Reference_Control_Type);
552 pragma Inline (Finalize);
554 type Constant_Reference_Type
555 (Element : not null access constant Element_Type) is
556 record
557 Control : Reference_Control_Type :=
558 raise Program_Error with "uninitialized reference";
559 -- The RM says, "The default initialization of an object of
560 -- type Constant_Reference_Type or Reference_Type propagates
561 -- Program_Error."
562 end record;
564 procedure Read
565 (Stream : not null access Root_Stream_Type'Class;
566 Item : out Constant_Reference_Type);
568 for Constant_Reference_Type'Read use Read;
570 procedure Write
571 (Stream : not null access Root_Stream_Type'Class;
572 Item : Constant_Reference_Type);
574 for Constant_Reference_Type'Write use Write;
576 -- Three operations are used to optimize in the expansion of "for ... of"
577 -- loops: the Next(Cursor) procedure in the visible part, and the following
578 -- Pseudo_Reference and Get_Element_Access functions. See Sem_Ch5 for
579 -- details.
581 function Pseudo_Reference
582 (Container : aliased Set'Class) return Reference_Control_Type;
583 pragma Inline (Pseudo_Reference);
584 -- Creates an object of type Reference_Control_Type pointing to the
585 -- container, and increments the Lock. Finalization of this object will
586 -- decrement the Lock.
588 type Element_Access is access all Element_Type;
590 function Get_Element_Access
591 (Position : Cursor) return not null Element_Access;
592 -- Returns a pointer to the element designated by Position.
594 Empty_Set : constant Set := (Controlled with HT => (null, 0, 0, 0));
596 No_Element : constant Cursor := (Container => null, Node => null);
598 type Iterator is new Limited_Controlled
599 and Set_Iterator_Interfaces.Forward_Iterator with
600 record
601 Container : Set_Access;
602 end record;
604 overriding function First (Object : Iterator) return Cursor;
606 overriding function Next
607 (Object : Iterator;
608 Position : Cursor) return Cursor;
609 overriding procedure Finalize (Object : in out Iterator);
611 end Ada.Containers.Hashed_Sets;