---
name: "Stack"
section: "3poc"
platform: "linux"
package: "objc-poc"
version: "3.1.26-2"
release: "Debian 3.0 (Woody)"
platforms: ["linux"]
url: "https://new.carta.tech/Stack/3poc"
---

# Stack(3poc)

Portable Object Compiler Stack class

## NAME

Stack - Portable Object Compiler Stack class

## 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**

\* new\
 \* new:\
 \* copy\
 \* deepCopy\
 \* emptyYourself\
 \* freeContents\
 \* free

**Interrogation**

\* depth\
 \* isEmpty\
 \* eachElement\
 \* topElement

**Adding**

\* push:\
 \* pop\
 \* swap\
 \* at:\
 \* removeAt:

**Printing**

\* printOn:

## 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.