Author: Markus Triska
The library(clp/clp_distinct) module provides the
following constraints:
- all_distinct(+Vars)
-
The variables in Vars are constrained to be pairwise
distinct. All variables must already be assigned domains (via vars_in/2
or vars_in/3)
when this constraint is posted.
- vars_in(+Vars,
+Domain)
-
Where Vars is a list of variables and Domain is a
list of non-negative integers. Each variable of Vars is
constrained to be in Domain.
- vars_in(+Vars,
+From, +To)
-
Where Vars is a list of variables, and 0 < From <
To. Each variable in Vars is constrained to be in the
discrete interval [From,To].
The all_distinct/1
constraint can detect various inconsistencies:
?- vars_in([X,Y,Z], [1,2]), all_distinct([X,Y,Z]).
No
In this example, 3 is assigned to Z without labeling any
variables:
?- vars_in([X,Y], [1,2]), vars_in([Z], [1,2,3]), all_distinct([X,Y,Z]).
X = _G180{1-2}
Y = _G183{1-2}
Z = 3 ;
The clp_distinct module can be used in conjunction with clp/bounds. All
relevant variables must still be assigned domains via one of the
vars_in predicates before all_distinct/1
can be posted:
:- use_module(library(bounds)).
:- use_module(library(clp_distinct)).
?- [X,Y] in 1..2, vars_in([X,Y], [1,2]), all_distinct([X,Y]), label([X,Y]).
X = 1
Y = 2 ;
X = 2
Y = 1 ;
