--- name: "Set" section: "3poc" platform: "linux" package: "objc-poc" version: "3.1.26-2" release: "Debian 3.0 (Woody)" platforms: ["linux"] url: "https://new.carta.tech/Set/3poc" --- # Set(3poc) Portable Object Compiler Set class ## NAME Set - Portable Object Compiler Set class ## Set **Inherits from:** Cltn ## Class Description **Set** instances are sets of objects with no duplicate (in the sense of **isEqual:** ) entries. The **Dictionary** class provides a key-value based interface to sets, and may sometimes be more convenient to use. To make Sets correctly work, the objects have to implement a pair of comparison methods which must act in a coordinated way : The message \[newElement isEqual:oldElement\]\ is expected to report whether *newElement* is equal to *oldElement* . The message \[newElement hash\]\ should return an integer which is equal for all objects for which **isEqual:** is true. Sets place all objects added to them into a hash table based on the results of sending the objects the **hash** message. **Set** assumes that, after being added to a set, objects, and their hash value, will not be changed. If any object does change, it will not be located properly in the set. The result of this is that the object will not be found or that it will be added to the set more than once. ## Adding Objects The methods **add:** , **addNTest:** , **filter:** , **replace:** and **add:ifDuplicate:** are used to add objects to a set. The difference between these methods is the procedure used in adding, how duplicates are handled and what value is returned. ## Method types **Creation** \* new\ \* new:\ \* with:\ \* with:with:\ \* add:\ \* copy\ \* deepCopy\ \* emptyYourself\ \* freeContents\ \* free **Interrogation** \* size\ \* isEmpty\ \* eachElement **Comparing** \* isEqual: **Adding** \* add:\ \* addNTest:\ \* filter:\ \* add:ifDuplicate:\ \* replace: **Removing** \* remove:\ \* remove:ifAbsent: **Testing Contents** \* includesAllOf:\ \* includesAnyOf: **Adding and Removing Contents** \* addAll:\ \* addContentsOf:\ \* addContentsTo:\ \* removeAll:\ \* removeContentsFrom:\ \* removeContentsOf: **Combining** \* intersection:\ \* union:\ \* difference: **Converting** \* asSet\ \* asOrdCltn **Using Blocks** \* detect:\ \* detect:ifNone:\ \* select:\ \* reject:\ \* collect:\ \* count: **Making elements perform** \* elementsPerform:\ \* elementsPerform:with:\ \* elementsPerform:with:with:\ \* elementsPerform:with:with:with: **Do Blocks** \* do:\ \* do:until: **Locating** \* find:\ \* contains:\ \* includes:\ \* occurrencesOf: **Printing** \* printOn: **Archiving** \* fileOutOn:\ \* fileInFrom:\ \* awakeFrom: ## Methods new \+ **new** Returns a new empty set. new: \+ **new** :(unsigned) *n* Returns a new empty set, which can hold at least *n* elements. copy \- **copy** Returns a new copy of the set. deepCopy \- **deepCopy** Returns a new copy of the set. The elements in the new set are deep copies of the elements in the original set. emptyYourself \- **emptyYourself** Empties all the members of the set (without freeing them). Returns the receiver. freeContents \- **freeContents** Removes and frees all the members of the set, but doesn't free the set itself. Returns the receiver. free \- **free** Frees the set, but not its elements. Returns **nil** . Do : set = \[\[set freeContents\] free\];\ if you want to free the set and its contents. size \- ( unsigned ) **size** Returns the number of elements in the set. isEmpty \- ( BOOL ) **isEmpty** Whether the number of objects in the set is equal to zero. eachElement \- **eachElement** Returns a sequence of elements in the set. seq = \[set eachElement\];\ while ((anElement = \[aSeq next\])) {\ /\* do something \*/\ }\ aSeq = \[aSeq free\];\ isEqual: \- ( BOOL ) **isEqual** : *set* Returns YES if *set* is a set, if *set* has the same number of elements as the receiver, and if each member of the contents of *set* is contained in the receiver's contents. add: \- **add** : *anObject* Adds *anObject* if it was not previously in the set, but doesn't inform the caller about the addition because the receiver is always returned. addNTest: \- **addNTest** : *anObject* Adds *anObject* if it was not previously in the set. Returns *anObject* if the addition takes place, otherwise returns **nil** . filter: \- **filter** : *anObject* The **filter:** method has a special purpose. If there is a matching object in the set, then *anObject* is freed, and the matching object is returned. Otherwise, *anObject* is added and returned. add:ifDuplicate: \- **add** : *anObject* **ifDuplicate** : *aBlock* Adds and returns *anObject* , if there was no duplicate previously in the set. Otherwise, this method evalutes *aBlock* and returns the matching object (the object that was already in the set). For example, the **filter:** method is equivalent to : \[ set add: anObject ifDuplicate: { \[anObject free\] }\];\ replace: \- **replace** : *anObject* If a matching object is found, then *anObject* replaces that object, and the matching object is returned. If there is no matching object, *anObject* is added to the receiver, and **nil** is returned. remove: \- **remove** : *oldObject* Removes *oldObject* or the element which matches it using **isEqual:** . Returns the removed entry, or **nil** if there is no matching entry. **Note:** The **remove:** method of the **OrdCltn** class is implemented to remove an exact match. The **Set** class uses a match in the sense of **isEqual:** instead. remove:ifAbsent: \- **remove** : *oldObject* **ifAbsent** : *exceptionBlock* Removes *oldObject* or the element which matches it using **isEqual:** . Returns the removed entry, or return value of *exceptionBlock* if there is no matching entry. For example, the method **remove:** is equivalent to : \[ set remove: oldObject ifAbsent: { nil } \];\ **Note:** The **remove:** method of the **OrdCltn** class is implemented to remove an exact match. The **Set** class uses a match in the sense of **isEqual:** instead. find: \- **find** : *anObject* Returns any element in the receiver which **isEqual:** to *anObject* . Otherwise, returns **nil** . contains: \- ( BOOL ) **contains** : *anObject* Returns YES if the receiver contains *anObject* . Otherwise, returns NO. Implementation is in terms of the receiver's **find:** method (which uses **isEqual:** and **hash** to decide whether the object is contained in the set). includes: \- ( BOOL ) **includes** : *anObject* This method is equivalent to **contains:** . occurrencesOf: \- ( unsigned ) **occurrencesOf** : *anObject* Returns 1 if *anObject* is in the receiver, otherwise returns 0. Implementation is in terms of the receiver's **find:** method (which uses **isEqual:** and **hash** ). printOn: \- **printOn** :(IOD) *aFile* Prints a list of the objects in the set by sending each individual object a **printOn:** message. Returns the receiver. fileOutOn: \- **fileOutOn** : *aFiler* Writes out non-nil objects in the Set on *aFiler* . Returns the receiver. fileInFrom: \- **fileInFrom** : *aFiler* Reads in objects from *aFiler* . Returns the receiver, which is a set that is not yet usable (until the set gets the **awakeFrom:** message). awakeFrom: \- **awakeFrom** : *aFiler* Rehashes the contents of the set, which was previously read from *aFiler* by the *fileInFrom:* method. The hash-values of the objects are possibly process or architecture dependent, so they are not stored on the filer. Rather, **awakeFrom:** recomputes the values.