Posted by aria2end on Aug 07, 2014; 3:13am
URL: https://forum.world.st/I-need-some-explaination-about-arguements-assignment-tp4772102.html

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