Put in minimal simpset to avoid excessive simplification,
just as in revision 1.9 of HOL/indrule.ML
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