SWI-Prolog -- fd

Documentation
- Reference manual
  - The SWI-Prolog library
    - library(clpfd): CLP(FD): Constraint Logic Programming over Finite Domains
      - CLP(FD) predicate index
        
        Reflection predicates
        
        fd_var/1
        
        fd_inf/2
        
        fd_sup/2
        
        fd_size/2
        
        fd_dom/2
- Packages

Availability::- use_module(library(clpfd)).

fd_size(+Var, -Size)

Reflect the current size of a domain. Size is the number of elements of the current domain of Var, or the atom sup if the domain is unbounded.