Help with from_to/2

[jgarte]

Hi,

What do I have wrong here in my code?

:- use_module(clpz).

from_to(From, To) :-
    From #=< To,
    NextFrom #= From + 1,
    from_to(NextFrom, To).


?- from_to(From, 5), label(From).

https://git.sr.ht/~whereiseveryone/prolog-scratch/tree/master/loop.pl#L6

[jgarte]

fixed 😊

:- use_module(clpz).


from_to(To, To).
from_to(From, To) :-
    From #< To,
    From #> 0,
    NextFrom #= From + 1,
    from_to(NextFrom, To).


?- from_to(From, 5).
%@    From = 5
%@ ;  From = 4
%@ ;  From = 3
%@ ;  From = 2
%@ ;  From = 1
%@ ;  false.

https://git.sr.ht/~whereiseveryone/prolog-scratch/tree/master/loop.pl#L12

[UWN]

Note the following irregularities:

?- from_to(1+1,To).
   To = 1+1
;  To = 3
;  To = 4
;  To = 5
;  ... .
?- from_to(unknown,To).
   To = unknown
;  error(domain_error(clpz_expression,unknown),unknown(unknown)-1).
?- from_to(From,1+1).
   From = 1+1
;  false.
?- from_to(From,2).
   From = 2
;  From = 1
;  false.

Rather

from_to(From, To) :-
   #From #=< #To,
   (  From = To
   ;  ...
   ).