Prod = FOL + types "*" 2 (infixl 20) arities "*" :: (term,term)term consts fst :: "'a * 'b => 'a" snd :: "'a * 'b => 'b" Pair :: "['a,'b] => 'a * 'b" ("(1<_,/_>)") rules fst "fst(<a,b>) = a" snd "snd(<a,b>) = b" end