Use a pair instead of a list to represent intervals

[pmoura]

Representing an interval using a pair, e.g. (X,Y) is more efficient than using a list, [X,Y]. To make it clear:

| ?- write_canonical([1,7]).
'.'(1,'.'(7,[]))

yes
| ?- write_canonical((1,7)).
','(1,7)

yes

I.e. accessing the upper limit in an interval is more costly with a list representation.

[mlliarm]

Thanks Paulo. This is a nice suggestion actually.

I might be needing some ways to get the first or the second element of the pair in the future. I know how to do this with lists, but I'm not sure how this could be possible with pairs. I'll look it up.

As the interval_arithmetic is I believe it can be changed easily to use pairs instead of lists. So I'll get to it.

[mlliarm]

I found this suggestion regarding my question above.

[pmoura]

I might be needing some ways to get the first or the second element of the pair in the future. I know how to do this with lists, but I'm not sure how this could be possible with pairs. I'll look it up.

Not sure I understand the problem. You can simply use unification as you're doing with lists. E.g.

    is_in((Xa, Xb), Number) :-
        Xa =< Number,
        Xb >= Number.

[mlliarm]

I might be needing some ways to get the first or the second element of the pair in the future. I know how to do this with lists, but I'm not sure how this could be possible with pairs. I'll look it up.

Not sure I understand the problem. You can simply use unification as you're doing with lists. E.g.

    is_in((Xa, Xb), Number) :-
        Xa =< Number,
        Xb >= Number.

I wasn't thinking about the predicates from interval_arithmetic, but for predicates to be created (see #10).

But it seems that unification should be enough. I'll have to think things harder, it seems. Thanks !

[mlliarm]

The interval_arithmetic library has been converted to use pairs (tuples) instead of lists.

So far all the created tests pass with 100%.

For this reason I'll close this issue.