README

Avoid record-inner constants in polymorphic definitions in Bali

The Bali package needs to insert a record extension into a type
class and define an associated polymorphic constant. There is no
elegant way to do this.

The existing approach was to insert every record extension into
the type class, defining the polymorphic constant at each layer
using inner operations created by the record package. Some of
those operations have been removed. They can be replaced by use
of record_name.extend if necessary, but we can also sidestep
this altogether.

The simpler approach here is to use defs(overloaded) once to
provide a single definition for the composition of all the type
constructors, which seems to be permitted. This gets us exactly
the fact we need, with the cost that some types that were
admitted to the type class have no definition for the constant
at all.

                       The Isabelle System Distribution

Version information

   This is some unidentified repository version of Isabelle.

   See the NEWS file in the distribution for details on user-relevant
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   Isabelle requires a regular Unix platform (e.g. GNU Linux) with the
   following additional software:
     * A full Standard ML Compiler (works best with Poly/ML 5.2.1).
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     * Perl (version 5.x).
     * GNU Emacs (version 21, 22, 23) or XEmacs (version 21.4.x)
       -- for the Proof General interface.
     * A complete LaTeX installation -- for document preparation.

Installation

   Binary packages are available for Isabelle/HOL and ZF for several
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   INSTALL as distributed with Isabelle for more information.

   Further background information may be found in the Isabelle System
   Manual, distributed with the sources (directory doc).

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   Lawrence C Paulson
   Computer Laboratory
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   JJ Thomson Avenue
   Cambridge CB3 0FD
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   or

   Tobias Nipkow
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   Technische Universitaet Muenchen
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   D-85748 Garching
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