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smalltalkpharo

Creating a method that prints while emptying the contents of a Stack

Given the class: 'AStack'

Object subclass: #AStack
    instanceVariableNames: 'elements'
...

It contains an OrderedCollection Object that holds it's 'element objects'

initialize 
super initialize.
elements := OrderedCollection new

It's member classes push and pop, respectively:

push: anObject 
self elements addFirst: anObject 

pop
^self elements removeFirst

I am trying to write a print method that uses timesRepeat to print the contents of the stack as well as empty it simultaneously. It calls the child class print method for each 'element' (print ^self name) and outputs it on the screen using 'Transcript'.

print
self size timesRepeat: [Transcript show: self pop print]

On the other side I have a class called 'SomeRandomObject' who's print method is:

print
Transcript show:self getName; cr

Workspace code:

| o1 o2 stk |

o1 := SomeRandomObject new.
o1 name: 'object1'.

o2 := SomeRandomObject new.
o2 name: 'object2'.

stk := AStack new.
stk push: o1.
stk push: o2.

stk print "prints and emptys stack"

Upon running I get the error:

Error: Instances of AStack are not indexable

How can I fix my code so the print method shows o1 and o2 name while popping them off the stack?

Solution

  • I cannot tell you exactly before you give me a full (at least bigger) stack trace, but I expect, that you wont have a #size method defined in your class which should be something like this:

    size
  ^ elements size