5.132. exactly
| DESCRIPTION | LINKS | GRAPH | AUTOMATON |
- Origin
- Constraint
- Synonym
.
- Arguments
- Restrictions
- Purpose
Exactly variables of the collection are assigned value .
- Example
-
The constraint holds since exactly variables of the collection are assigned value .
- Typical
- Symmetries
Items of are permutable.
An occurrence of a value of that is different from can be replaced by any other value that is also different from .
- Systems
occurence in Choco, count in Gecode, count in JaCoP, count in SICStus.
- See also
generalisation: Β ( replaced by and replaced by of ).
implies: Β ( replaced by ), Β ( replaced by ).
- Keywords
characteristic of a constraint: automaton, automaton with counters.
constraint network structure: alpha-acyclic constraint network(2).
- Arc input(s)
- Arc generator
-
- Arc arity
- Arc constraint(s)
- Graph property(ies)
-
- Graph model
Since each arc constraint involves only one vertex ( is fixed), we employ the arc generator in order to produce a graph with a single loop on each vertex.
PartsΒ (A) andΒ (B) of FigureΒ 5.132.1 respectively show the initial and final graph associated with the Example slot. Since we use the graph property, the loops of the final graph are stressed in bold. The constraint holds since exactly two variables are assigned value 4.
Figure 5.132.1. Initial and final graph of the constraint
(a) (b)
- Automaton
FigureΒ 5.132.2 depicts the automaton associated with the constraint. To each variable of the collection corresponds a 0-1 signature variable . The following signature constraint links and : .
Figure 5.132.2. Automaton of the constraint
Figure 5.132.3. Hypergraph of the reformulation corresponding to the automaton of the constraint
