简单约束逻辑编程示例 CLP(Q) 在 Prolog 中给出错误

Question

I've started to learn Prolog and I follow the RIPTutorial PDF. At the Constraint Logic Programming CLP(Q) section, it says:

Constraint Logic Programming CLP(Q) implements reasoning over rational numbers

Example:

?- { 5/6 = X/2 + 1/3 }.
X = 1.

When I've tried this line on SWI-Prolog on Windows, it gave:

ERROR: Unknown procedure: {}/1 (DWIM could not correct goal)

The same line on commandline SWI-Prolog-7.2.0 on macOS gives:

ERROR: toplevel: Undefined procedure: {}/1 (DWIM could not correct goal)

How to get the expected output of X = 1. ?

Answer 1

Using SWI-Prolog .

As noted in the comments you need to load the code for CLP(Q) first.

?- use_module(library(clpq)).
true

Then enter the query as in the example.

?- {5/6 = X/2 + 1/3}.
X = 1.