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sortcltn Specification Sheet

Portable Object Compiler (c) 1997,98. All Rights Reserved.

SortCltn

Inherits from: Cltn

Class Description

SortCltn (alias SortedCollection) instances are groups of objects that are kept in sorted order in a tree (by default, the first object is the smallest with respect to compare:). Inserting and searching objects in such a sorted collection can be faster than using, say an OrdCltn object collection.

Creating An Instance

The method new creates an instance that sorts its elements with respect to compare:. The method newDictCompare sends dictCompare: messages to compare pairs of elements. Finally, the method sortBy:: creates a SortCltn that will sort its contents with respect to an arbitrary Block.

Adding Objects

Normally, you insert an object with the add: method. This method allows you to add an object to the collection, even when it is equal to an element in the collection (when the comparison method returns zero; because you can use a different method than compare:, this doesn't necessarily mean that isEqual: returns YES).

You can also choose not to add duplicate entries. The addNTest: method adds if the object was absent and returns a value that can be used to test whether the object was found or not. The filter: method frees a new entry when it's a duplicate. The replace: method always replaces duplicates (returning the object that was previously in the collection).

Sorting collections

One use of SortCltn instances, is to sort collections of objects. For example,

aSortCltn = [[SortCltn new] addAll:aCltn];
will sequence of the contents of aCltn and will add the members of the collection to a new SortCltn instance. This is equivalent to sorting the collection. To obtain a sorted OrdCltn instance (as opposed to a SortCltn), simply convert back like this,

aCltn = [[OrdCltn new] addAll:aSortCltn];
To filter out duplicate entries, it's also possible to insert a Set instance in the conversion process.

Method types

Creation

Interrogation

Comparing

Adding

Removing

Testing Contents

Adding and Removing Contents

Combining

Converting

Using Blocks

Making elements perform

Do Blocks

Locating

Printing

Archiving

Methods

new

+new
Returns a new instance that sorts its contents with respect to compare:.

new:

+new:(unsigned)n
For this class, this method does not differ from new.

newDictCompare

+newDictCompare
Returns a new instance that sorts its contents with respect to dictCompare:.

sortBy:

+sortBy:sortBlock
Returns a new instance that sorts its contents with respect to sortBlock. This block should take two objects a and b as argument, and return a positive value if a is greater than b, or zero if a and b are equal, and a negative value if a is less than b.

id c;
int r;
c = [SortCltn sortBy:{ :a:b | [a compare:b] }];

sortBlock:

+sortBlock:sortBlock
Same as sortBy:.

Note: There is a SortedCollection method with a similar name in Squeak.

newCmpSel:

+newCmpSel:(SEL)aSel
For backwards compatibility only. sortBy: provides a more powerful mechanism to sort given an arbitrary sort block.

copy

-copy
Returns a new copy of the object (without copying the elements).

deepCopy

-deepCopy
Returns a new copy of the object. The elements in the new copy are deep copies of the elements in the original object.

emptyYourself

-emptyYourself
Empties all the members of the object (without freeing them). Returns the receiver.

freeContents

-freeContents
Removes and frees the contents of the object, but doesn't free the object itself. Returns the receiver.

free

-free
Frees the object, but not its contents. Returns nil. Do :

aSort = [[aSort freeContents] free];
if you want to free the object and its contents.

size

- (unsigned)size
Returns the number of elements in the object.

isEmpty

- (BOOL)isEmpty
Whether the number of elements is equal to zero.

eachElement

-eachElement
Returns a sequence of sorted elements. The first element in the sequence is the smallest with respect to the ordering.

aSeq = [aSort eachElement];
while ((anElement = [aSeq next])) {
    /* do something */
}
aSeq = [aSeq free];

hash

- (unsigned)hash
Returns a hash value based on the receiver's address and the results of sending the hash message to the contents.

isEqual:

- (BOOL)isEqual:aSort
Returns YES if aSort is an SortCltn instance, and if each member of its contents responds affirmatively to the message isEqual: when compared to the corresponding member of the receiver's contents.

add:

-add:anObject
Adds anObject to the receiver, keeping the contents of the object sorted. Duplicate entries are allowed. Returns the receiver.

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
If anObject compares equally to some object in the contents of the receiver, then anObject is freed, and the matching object is returned. Otherwise, anObject is added and returned.

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 that matches (when the compare method returns zero). Returns the removed entry, or nil if there is no matching entry.

Note: Not implemented

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.

printOn:

-printOn:(IOD)aFile
Prints a comma separated list of the objects in the set by sending each individual object a printOn: message. Returns the receiver.

fileOutOn:

-fileOutOn:aFiler
Writes the tree and all its elements to aFiler. Returns the receiver.

fileInFrom:

-fileInFrom:aFiler
Reads the tree and all its elements from aFiler. Returns the receiver.