Re: [Pharo-users] I need some explaination about arguements assignment

Aug. 7, 2014

      Hi Aria,

Welcome to Smalltalk and Pharo. I havenât tried executing your code but I have a couple observations. I believe that the problem is in attempting to assign to a passed-in argument. As far as I know, the following is illegal:

foo: aString
	aString := aString , â barâ.

Method (and block) arguments may be sent messages, but may not be assigned. A common approach to what it appears you are doing is to use a WriteStream. For example:

startRecursion
	| stream |
	stream := WriteStream on: String new.
	self recurseOnStream: stream level: 4.
	Transcript show: stream contents.

recurseOnStream: aStream level: anInteger
	anInteger <= 0 ifTrue: [^self].
	anInteger timesRepeat: aStream tab.
	aStream nextPutAll: anInteger printString; cr.
	self recurseOnStream: aStream level: anInteger - 1.

Let us know if this helps resolve the issue.

James Foster

On Aug 6, 2014, at 8:13 PM, aria2end <aria2end@gmail.com> wrote:
...
Hello, I am new to smalltalk and I would really appreciate your help so I can
better use and understand Pharo.
So here is the problem, I wanted to implement a function to get the value of
my tree struct nodes in a recursive manner and I wanted to concatenate them
to a String ( aText ) and later show them on the Transcript.
showLists 
       | aText | 
        aText  :=  lol level,  (String with: Character cr). 
       self recursiveShowLists: lol withText: aText tabsNumber: 1.
recursiveShowLists: aLoL withText: aText tabsNumber: aNumb 
       | counter index | 
       aLoL lols isEmpty 
               ifFalse: [ 
                       counter := 1. 
                       [ counter <= aNumb ] 
                               whileTrue: [ 
                                       aText := aText , (String with:
Character tab). 
                                       counter := counter + 1 ]. 
                       index := 1. 
                       aNumb := aNumb + 1. 
                       LoL lols do: [ :each | aText := aText , each level ,
(String with: Character cr) ]. 
                       ]
Without having the last line ( LoL lols do: ... ) everything works fine but
when I include it and as soon as debugger reaches to [counter <= aNumb ] and
wants to evaluate it, my arguments start to act weird. aText will become nil
and aNumb will hold te value of aText!
I fixed this issue by adding another temporary variable ( copyText ) and
instead of direct assignment of aText I used the copyText:
recursiveShowLists: aLoL withText: aText tabsNumber: aNumb 
       | counter index copyText | 
       copyText := aText.
       aLoL lols isEmpty 
               ifFalse: [ 
                       counter := 1. 
                       [ counter <= aNumb ] 
                               whileTrue: [ 
                                       copyText := copyText , (String with:
Character tab). 
                                       counter := counter + 1 ]. 
                       index := 1. 
                       aLoL lols do: [ :each | copyText := copyText , each
level , (String with: Character cr) ] ]
I really like to know the reason behind this issue,  I appreciate all the
explanations.
Thanks,
Aria
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