Labeling and variable ordering

Several predicates are provided for choosing variables and assigning values to variables.

• indomain(?V) V is instantiated to a value in the domain. On backtracking, the domain variable is instantiated to the next value in the domain.

• deleteff(-V,+Vars,-Rest) Chooses first a domain variable V from Vars with the minimum domain. Rest is a list of domain variables without V.

• deleteffc(-V,+Vars,-Rest) Chooses first a variable that has the smallest domain and that participates in a largest number of constraints.

• labeling(+Vars) Instantiates the variables in Vars one by one.

• labeling_ff(+Vars)
• labelingff(+Vars) Instantiates the variables in Vars by using deleteff/3 to choose variables.

• labeling_ffc(+Vars)
• labelingffc(+Vars) Instantiates the variables in Vars by using deleteffc/3 to choose variables.