Updating list has effect on second list

[xota]

I'm surprised to see that when I "make a copy" of a list with "set list_copy to list_original", updating either of the two lists updates the other too.
The copy was intended to check further down the code to check if the original list was altered.

Would be nice to have some explanation on to treat the copies independently.

[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 S…

[xota]

Thank you for ultra fast pointing me to to the very helpful post of Brian.