Re: [isabelle] Defining finite list functions recursively
Thanks Alex, that did the trick nicely. It seems to be holding up for
defining mutually-recursive lists as well.
On Jun 12, 2008, at 12:40 AM, Alexander Krauss wrote:
I'm having problems proving termination of the well-founded
recursive function xs_strm defined below, and other functions like
Good to see that you are driving all available tools to their limits
and beyond, as usual :-) But it might actually work...
The problem is that nth_take_cong has the premise about the lengths
being equal. In the function definition, a "recursive call" will be
generated by this premise because the instance occuring contains the
function being defined. But this simplifies away in your manual
proof because "length (strm_to_list n f)" does not depend on f.
So you need just one more cong rule to tell function about this:
"n = n' ==> length (strm_to_list n f) = length (strm_to_list n' f')"
Then it works.
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