what are the two stars in a list?
[53, 5, 1, 53, 97, 115, 53, 50, 52, 121, 55, 56, 55, 97, 4, 1, 98, **]
I tried searching but no success.
Asked
Active
Viewed 340 times
6
-
Newer versions of SWI no longer use `**` – false Aug 22 '14 at 17:04
1 Answers
9
The stars indicate that the term contains itself, e.g.
?- X = f(X).
X = f(**).
?- L = [53, L].
L = [53, **].
This is the case at least in older versions of SWI-Prolog. See also https://lists.iai.uni-bonn.de/pipermail/swi-prolog/2009/001707.html.
Kaarel
- 10,554
- 4
- 56
- 78