error(instantiation_error,number)

[jgarte]

Hi,

I get this error when trying to run the below code:

%@    error(instantiation_error,number).

Could this be an incompatibility between the lists and clpz library or a mistake in my logic?

Any help is much appreciated.

:- use_module(clpz).
:- use_module(format).
:- use_module(lists).

sum_chord([N1, N2, N3, N4]) :-
    [N1, N2, N3, N4] ins 0..11,
    sum_list([N1, N2, N3, N4], 26).

label_chords(Chord) :-
    sum_chord(Chord),
    label(Chord).


render(Chord, File) :-
    open(File, write, Out),
    forall(label_chords(Chord), format(Out,'~w ~w ~w ~w~n', Chord)),
    close(Out).

go :- render([N1, N2, N3, N4], 'chords.txt').

?- go.

More context:

I was trying to generate chords that sum to 26 inspired by this article:

https://www.editions75.com/texts/Chords_within_chords.pdf

[guregu]

Use sum/3 from clpz instead of sum_list/2
https://www.scryer.pl/clpz.html#sum/3

[jgarte]

Nice! That fixed it.

How could I have deduced this?

I guess what I learned is that predicates in lists will not work with clpz unless they have explicit support?

[guregu]

The instantiation error you got means that you passed a variable to somewhere that expected a non-variable. clpz terms are variables until you label them or they are constrained enough to become a single number. But yeah, in general you want to try to use predicates from the clpz module when available.

[jgarte]

chords.pdf

All these chords sum to 26. Yay!

https://git.sr.ht/~whereiseveryone/prolog-scratch/commit/43e7a55b72c133334ae01a752b49d7b5fe5bcd80

[infradig]

So the search for the lost chord continues...