SWI-Prolog -- find_chr_constraint/1

Documentation
- Reference manual
  - CHR: Constraint Handling Rules
    - Debugging CHR programs
      - CHR Debugging Predicates
        
        chr_trace/0
        
        chr_notrace/0
        
        chr_leash/1
        
        chr_show_store/1
        
        find_chr_constraint/1
- Packages

find_chr_constraint(-Constraint)

Returns a constraint in the constraint store. Via backtracking, all constraints in the store can be enumerated.