Hi,
the simplifier supports AC normalisation (see Sec. 7.5.5.2 in the
description manual). AC normalisation would sort multiple occurrences of
the same operant next to each other. Therefore these multiple
occurrences can then be removed by providing 2 idempotency rewrite rules:
f x x = x
f x (f x y) = f x y
This provides a very high level simple way to do what you want, I believe.
If you want something lower level, more efficient with finer control,
you could use "sort" from structure "AC_Sort". It provides a conversion
that does what you want if instantiated properly. However, I never used
it myself, so I don't have first hand experience with it.
There is also the structure "AC" from refute. However, I believe in
contrast to "AC_Sort", there is no direct support for idempotency in "AC".
Cheers
Thomas
On 21.02.2018 18:34, Mario Xerxes Castelán Castro wrote:
> Hello.
>
> Is there an existing tactic for removing multiple appearances of an
> operand under an operator «f» that has the property «f x x = x» and is
> associative-commutative? For example, conjunction and disjunction.
>
> If not, I can write one for HOL4, but I do not want to duplicate
> existing work.
>
> Thanks.
>
>
>
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