%-

tydecl case = Nominative | Accusative | Dative | Genitive | Instrumental

tydecl gender = Masculine | Feminine | Neuter

tydecl number = Singular | Plural

; demonstrative pronouns
; "this" or "these"
(:def decline
  (:lambda x (case, gender, number)
    (:match x
      [((Nominative|Accusative), _, Plural) "þas"]
      [((Nominative|Accusative), Neuter, Singular) "þis"]
      [((Genitive|Dative|Instrumental), Feminine, Plural) "þisse"]
      [(Dative, (Masculine|Neuter), Singular) "þissum"]
      )))