Re: [isabelle] Different behavior in Jedit and Emacs

On changeset 693d8d7bc3cd, the issue is somehow hidden in the different conditions (if null ts ...) of these two source code positions below.

Maybe, one of two authors of this file could take a closer look at this point.


diff -r 693d8d7bc3cd src/HOL/Tools/Function/size.ML
--- a/src/HOL/Tools/Function/size.ML    Fri Jan 20 09:28:54 2012 +0100
+++ b/src/HOL/Tools/Function/size.ML    Fri Jan 20 17:47:23 2012 +0100
@@ -105,7 +105,7 @@
              else us, i, j + 1))
               (cargs ~~ cargs' ~~ Ts) ([], 0, k);
         val t =
- if null ts andalso (not b orelse not (exists (is_poly thy) cargs')) + if null ts andalso (not b orelse not (exists (is_poly thy) cargs'))
           else foldl1 plus (ts @ [HOLogic.Suc_zero])
@@ -182,7 +182,7 @@
         HOLogic.mk_Trueprop (HOLogic.mk_eq
           (size_const $ list_comb (Const (cname, Ts ---> T),
              map2 (curry Free) tnames Ts),
-           if null ts then
+           if null ts then
            else foldl1 plus (ts @ [HOLogic.Suc_zero])))

On 01/20/2012 05:16 PM, Brian Huffman wrote:
Congratulations Björn, you've found a soundness bug in the datatype
package! At least in quick and dirty mode, the datatype package
generates some unproven "theorems" that are contradictory. Here's a
proof of False that works if you are in quick and dirty mode:

datatype 'a tree = leaf "'a" | node "nat =>  'a tree"
datatype 'a dtype  = constr "'a tree"

lemma "False"
proof -
   have "dtype_size fa (constr tree) = Suc 0"
     unfolding dtype_size_def by simp
   also have "dtype_size fa (constr tree) = 0"
     by (rule dtype.size(1))
   finally show "False"
     by simp

This is a good reminder why quick and dirty mode is a bad idea. We
should definitely make sure that the default is set to "off" in all
future releases, for both ProofGeneral and jEdit.

- Brian

On Fri, Jan 20, 2012 at 4:46 PM, Lukas Bulwahn<bulwahn at>  wrote:
I tried it myself as well on the development version (changeset 693d8d7bc3cd
- the current tip):
It works if you switch on quick_and_dirty, but it fails if you switch it

This succeeds:

ML {* quick_and_dirty := true *}

datatype 'a dtype  = constr "'a tree"

But this fails:

ML {* quick_and_dirty := false *}

datatype 'a dtype  = constr "'a tree"

Just a short explanation, why this differs:
In quick-and-dirty mode, we actually skip proofs, which are automatically
generated by packages, and just provide the theorems
without proof.
Switching it off, the package will actually perform the proof, but in the
case mentioned here, this proof method fails.

It seems that your default settings actually differ on the two interfaces,
JEdit and Emacs.

We will have to investigate why the proof method actually breaks down in
this case.


On 01/20/2012 04:30 PM, Tobias Nipkow wrote:
Just as another data point: I tried the development version with emacs
and it works.


Am 20/01/2012 16:09, schrieb Björn Bartels:
Hi all,
we just came across  the following problem when using the datatype
command. The following datatype definition works when using Jedit but does
not work when using Emacs as interface. In the previous distribution the
example used to work with Emacs as well.

theory test
imports Main

datatype 'a tree =
            leaf "'a"
          | node "nat \<Rightarrow>    'a tree"

datatype 'a dtype  = constr "'a tree"


When using Emacs, we get the following error message:

*** Proof failed.
*** dtype_size fa (constr tree) = 0
***  1. Suc 0 = 0
*** 1 unsolved goal(s)!
*** The error(s) above occurred for the goal statement:
*** dtype_size fa (constr tree) = 0

Thanks for any suggestions!

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