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I understand that Sort is destructive, and I have no issue with that. My issue is that I have two separate lists in the program, say list1 and list2. And when I call (setf list2 (sort list2 #'string)), in addition to sorting list2, I find that the contents of list1 have changed. This seems very odd ...

I recently wrote a cryptarithmetic solver for a school project and have been tweaking it to try to improve it for fun. In the program, it takes the two operands and sum as lists, and creates a fourth list of unique variables in the problem. For example, from the problem EAT + THAT = APPLE, it create...