Dear list,

I have seen this nice package for interval arithmetic:

```
:- use_module(library(clpBNR)).
example :-
X = 1,
Y::real(-0.1, 0.1),
{Z == X + Y},
writeln(sum: Z).
```

What I am wondering is (I apologize if the question is trivial): The package clpBNR implements the arithmetic as a constraint solver, which is nice, but way to much for me (and maybe too slow, I don’t know). Is there a simpler, “functional” alternative, basically one that would just duplicate is/2. In my use case, the LHS of ==/2 is always a variable, and everything on the RHS is instantiated.

Best regards,

Matthias