Need help writing simple insertion sort in Prolog - continue getting errors

Question

I have a simple assignment of writing an insertion sort in Prolog. Here are the instructions:

(10 points) insertionSort(List, Sorted) Write an insertion sort program in prolog. You may assume all elements of the list are numbers.

Basically, I have to give it a list, and it will return a list of the sorted values. After completely failing when writing it myself (though mine seems similar to everything else - see my code posted below), I decided to go get help on the internet. I have literally tried every example of an insertion sort I have found on the internet for prolog...and not a SINGLE ONE worked. Not a single one.

I don't understand why. Maybe it's because I am supposed to be using SWI prolog.

I keep getting the two following errors:

ERROR: toplevel: Undefined procedure: insertionSort/2 (DWIM could not correct goal)

ERROR: toplevel: Undefined procedure: insertionSort/3 (DWIM could not correct goal)

I am so fed up with this stupid error. It is in no way helpful. How come when I do the exact same thing I do to call another simple procedure (a sum procedure thing), by compiling the file and then calling the thing I want, it works, but with this insertionSort one, it doesn't? I am positive I am not calling it incorrectly.

Here is my code so far. Not like it does anything.

insertionSort([],[]) :-
   !.
insertionSort([H|T], X) :-
   insertionSort(T, Y),
   insert(H, Y, X).

insert(A, [], [A]) :-
   !.
insert(A, [H|T], [A|L]) :-
   A =< H,
   insert(H, T, L).
insert(A, [H|T], [H|L]) :-
   A > H,
   insert(A, T, L).

Like I said, I've already tried probably 2 dozen + examples on the internet, and all of them come up with error messages, so if your answer is to link me to something, I can guarantee I already exhausted it (like this: Prolog insertion sort - doesn't that look like it would work? Well, it doesn't.)

Please, I am so frustrated. Any help is appreciated.

Need help writing simple insertion sort in Prolog - continue getting errors

Answers (1)

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