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(* Title: HOL/AxClasses/Tutorial/ProdGroupInsts.thy
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ID: $Id$
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Author: Markus Wenzel, TU Muenchen
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Lift constant "<*>" to cartesian products, then prove that the
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'functor' "*" maps semigroups into semigroups.
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*)
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ProdGroupInsts = Prod + Group +
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(* direct products of semigroups *)
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defs
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prod_prod_def "p <*> q == (fst p <*> fst q, snd p <*> snd q)"
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instance
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"*" :: (semigroup, semigroup) semigroup
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{| simp_tac (!simpset addsimps [assoc]) 1 |}
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end
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