Prolog-return all triples of elements in the ring Zm which satisfy the property x + y = z- Arguments are not sufficiently instantiated

Question

I am trying to Implement plus(X,Y,Z) , which should return all triples of elements in the ring Z_m that satisfy the property X + Y = Z, etc.

Here is my codes:

plus(X,Y,Z):-read(M),A is mod(X,M),B is mod(Y,M),Sum is A+B,Z is Sum mod M.
times(X,Y,Z):-read(M),A is mod(X,M),B is mod(Y,M),Product is A*B,Z is Product mod M.

But it is said:

Arguments are not sufficiently instantiated
In:
   [2] _1430 is _1436 mod 5
   [1] plus(_1490,_1492,_1494) at  line 10

I am new to Prolog and I feel so clueless...

Why are you using `read`? `plus/3` is already available: https://www.swi-prolog.org/pldoc/man?predicate=plus/3 — brebs, Sep 02 '22 at 11:28
Can you put your complete program here, especially including the call? — Topological Sort, Sep 02 '22 at 13:43

score 1 · Accepted Answer · answered Sep 01 '22 at 08:19

1

You've only shown a tiny portion of the program.

The usual choices are:

Instantiate the variables (obvious)
Use freeze or when to delay usage
Use e.g. clpfd or clpBNR, which can handle arithmetic on vars

answered Sep 01 '22 at 08:19

brebs

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sry i am not sure i understand...the first option is the easiest way, right? – Miu Sep 01 '22 at 08:31
to be honest I thought that's all I need to write down:( – Miu Sep 01 '22 at 08:33

Prolog-return all triples of elements in the ring Zm which satisfy the property x + y = z- Arguments are not sufficiently instantiated

1 Answers1