SWI-Prolog -- #\ / 2

Documentation
- Reference manual
  - The SWI-Prolog library
    - library(clpfd): CLP(FD): Constraint Logic Programming over Finite Domains
      - CLP(FD) predicate index
        
        Reification predicates
        
        #\/1
        
        #<==>/2
        
        #==>/2
        
        #<==/2
        
        #/\/2
        
        #\//2
        
        #\/2
        
        zcompare/3
- Packages

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

Source

Either P holds or Q holds, but not both. See reification (section A.9.12).