rules:
  predicate:
    - tautology
    - contradiction
    - identifier
    - qualified_identifier
    - var
    - not
    - and
    - or
    - eq
    - neq
    - lt
    - lte
    - gt
    - gte
    - in
    - exists
    - intersect
    - subset
    - superset
    - match
    - native
    - empty
    - has_size
    #jeny(predicate) - ${op_name}
  tautology:
    - [ true ]
  contradiction:
    - [ false ]
  identifier:
    - [ name ]
  qualified_identifier:
    - [ name, name ]
  var:
    - [ formaldef, semantics ]
  not:
    - [ predicate ]
  and:
    - [ predicate+ ]
  or:
    - [ predicate+ ]
  eq:
    - [ term, term ]
  neq:
    - [ term, term ]
  lt:
    - [ term, term ]
  lte:
    - [ term, term ]
  gt:
    - [ term, term ]
  gte:
    - [ term, term ]
  in:
    - [ varref, term ]
  intersect:
    - [ term, term ]
  subset:
    - [ term, term ]
  superset:
    - [ term, term ]
  match:
    - [ term, term, options ]
  empty:
    - [ term ]
  has_size:
    - [ term, term ]
#jeny(predicate)   ${op_name}:
#jeny(predicate)     - [ TODO ]
  term:
    - varref
    - literal
    - placeholder
    - opaque
    - exists
  varref:
    - qualified_identifier
    - identifier
    - var
  native:
    - [ "::Proc" ]
  literal:
    - "::Object"
  placeholder:
    - "::Predicate::Placeholder"
  opaque:
    - "::Object"
  exists:
    - "::Object"
  handler:
    - "::Object"
  options:
    - "::Hash"
  name:
    !ruby/regexp /^[a-zA-Z0-9_]+[?!]?$/
  semantics:
    !ruby/regexp /^(dig)$/
  formaldef:
    - string_formaldef
    - array_formaldef
  string_formaldef:
    - "::String"
  array_formaldef:
    - "::Array"