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stack Specification Sheet

Portable Object Compiler (c) 1998. All Rights Reserved.

Stack

Inherits from: Cltn

Class Description

Stack instances are collections that maintain their entries in LIFO (last in first out) order. Although Stacks are most often controlled by the push: and pop methods, the class also provides for random access of the stack, through the at: and removeAt: methods. Note that the indices are relative to the top (last added) item on the stack, which is the opposite of how the OrdCltn class works.

Method types

Creation

Interrogation

Adding

Printing

Methods

new

+new
Returns a new empty stack.

new:

+new:(unsigned)n
Returns a new empty stack, that can hold n objects.

copy

-copy
Returns a new copy of the stack.

deepCopy

-deepCopy
Returns a new copy of the stack. The members in the new stack are deep copies of the members in the original stack.

emptyYourself

-emptyYourself
Removes all the members of the stack (without freeing them). Returns the receiver.

freeContents

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

free

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

aCltn = [[aCltn freeContents] free];
if you want to free the collection and its contents.

depth

- (unsigned)depth
Returns the number of objects on the stack.

isEmpty

- (BOOL)isEmpty
Whether the number of objects on the stack is equal to zero.

eachElement

-eachElement
Returns a sequence of the elements in the collection.

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

topElement

-topElement
Returns the top element on the stack, without removing it. Returns nil if there are no elements on the stack.

push:

-push:anObject
Pushes anObject on the stack, so that it becomes the top of the stack. Returns self.

pop

-pop
Pops the top of the stack and returns it. Returns nil if the stack is empty.

swap

-swap
Exchanges the top two stack items and returns the receiver. Generates an exception if the stack is not at least two items deep.

at:

-at:(unsigned )anOffset
Returns the object at anOffset. Note that the top of the stack is at offset 0.

removeAt:

-removeAt:(unsigned )anOffset
Removes the object at anOffset. Note that the top of the stack is at offset 0.

printOn:

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