I gave it my Popper append example:

hakank.
'''
Here's another problem for you:
pos(f([],[],[])).
pos(f([],[a],[a])).
pos(f([],[a,b],[a,b])).
pos(f([a],[b],[a,b])).
pos(f([c,d],[e,f],[c,d,e,f])).
neg(f([],[b],[a])).
neg(f([a],[],[])).
neg(f([a],[b],[b])).
neg(f([a],[b],[b,a])).
neg(f([a,b],[c,d],[a,c,d])).
'''

GPT4:
'''
The pattern is that the function f takes two input lists and returns a new list, which is the concatenation of the two input lists.

For example:

Input: ([], [a, b]), Output: [a, b]
Input: ([a], [b]), Output: [a, b]
Input: ([c, d], [e, f]), Output: [c, d, e, f]
'''

Great!