Add listB to listA - and after changing listB => listA also changes?

[frank_claessen]

Is this supposed to happen?

At first - before the pause, listA looks normal and as to be expected.

But than, changing listB also affects listA ??

[ego-lay_atman-bay]

I copied a list to another variable, and then when I change the copy, it changes the original too!

Short answer: You didn't copy the list to the variable, you gave the same list another name. [The pictures below are a lie. See below the divider -------- for the full story.] Here's what it looks like: [untitled%20script%20pic] [Stage] The list is made of pairs, each of which points to one list item (left half) and to another pair (right half). The right half of the last pair is a special empty-list object. [untitled%20script%20pic%20(2)] The variable FOO points to the list, and the …

[frank_claessen]

So setting I understand that we create a pointer. That’s why we use id_of to make a real copy. I hadn’t expected the same to happen with adding.

I can code around it, no problem.

Thx

[bh]

I hadn’t expected the same to happen with adding.

It has nothing to do with setting or adding. LISTA has LISTB as an item, the actual LISTB. That’s true no matter how you use those lists later.