Re: [isabelle] Recursion through Types

Dear Tjark,

I don't know how far the following solution is applicable to your
setting, but a somehow similar problem (and two different solutions)
were proposed in the mailing list by J. Harrison a while ago, for the
definition of determinants of matrices of dimension n, in terms of
determinants of matrices of size "n - 1":

Hope it helps,



On Fri, Oct 18, 2013 at 7:29 PM, Tjark Weber <webertj at> wrote:
> Hi,
> There is a trick (due to John Harrison) to encode the dimension N of,
> e.g., N-bit words with a type argument.  The word libraries in
> Isabelle/HOL and HOL4 are based on this approach.
> In this setting, what is the recommended way to define a function that
> performs recursion over N, i.e., whose result for an (N+1)-bit word is
> naturally expressed in terms of its result for an N-bit word?
> Best,
> Tjark

Jesús María Aransay Azofra
Universidad de La Rioja
Dpto. de Matemáticas y Computación
tlf.: (+34) 941299438 fax: (+34) 941299460
mail: jesus-maria.aransay at ; web:
Edificio Luis Vives, c/ Luis de Ulloa s/n, 26004 Logroño, España

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