hidden types in (is)/2 while computing with rational numbers

[ghost]

There is some hidden types somewhere. Possibly rdiv(A,1) is displayed as A. Or somewhere inbetween converted to A. I get this “error”. First it tells me the sub result is 3.

Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.19)

?- X is 13 rdiv 4 - (1 rdiv 2)*(1 rdiv 2).
X = 3.

Now I use the sub result to get the final result:

?- Y is 1/3.
Y = 0.3333333333333333.

If I do it in one go I get the following result:

?- Z is 1/(13 rdiv 4 - (1 rdiv 2)*(1 rdiv 2)).
Z = 1 rdiv 3.

Thats a little strange.

[JanWielemaker]

Same as your message on discourse https://swi-prolog.discourse.group/t/future-of-support-for-rational-numbers/1779/6

[JanWielemaker]

This issue has been mentioned on SWI-Prolog. There might be relevant details there:

https://swi-prolog.discourse.group/t/future-of-support-for-rational-numbers/1779/10

[JanWielemaker]

I now see what you mean. This indeed is a bug. I'll re-open it for the record, but I think it is a better idea to property support rationals than fixing this. And no, screen shots have no added value, so please stop using them.

[JanWielemaker]

This issue has been mentioned on SWI-Prolog. There might be relevant details there:

https://swi-prolog.discourse.group/t/using-screen-shots-and-images/1783/2

[ghost]

The (^)/2 operator is also affected:

?- X is (13 rdiv 4 - (1 rdiv 2)*(1 rdiv 2))^(-1).
X = 1 rdiv 3.

?- Y is 13 rdiv 4 - (1 rdiv 2)*(1 rdiv 2), X is Y^(-1).
Y = 3,
X = 0.3333333333333333.