Isabelle component exporting Isabelle proofs to Dedukti

Dependencies

• Isabelle2023

• one dk file checker among:

  • kocheck
  • dkcheck 2.7
  • lambdapi >= 2.2.1

• or one lp file checker among

  • lambdapi >= 2.2.1

Prerequisites

• Isabelle

  • Download Isabelle2023

  • Unpack and run Isabelle2023/bin/isabelle jedit at least once, to ensure that everything works (e.g. see Documentation panel with Examples).

  • The command-line executable isabelle is subsequently used without further qualification, in practice it works like this:

    • explicit executable path (relative or absolute) on the command-line

    • or: insert the absolute path of the Isabelle bin directory in $PATH

    • or: install references to the Isabelle executables in another directory mentioned in $PATH

• isabelle_dedukti

  • Clone the repository:

    git clone https://github.com/Deducteam/isabelle_dedukti.git

  • Register it to Isabelle as a user component, by providing a (relative or absolute) directory name as follows:

    isabelle components -u $path_to_isabelle_dedukti

    The resulting configuration is in $ISABELLE_HOME_USER/etc/components (e.g. use Isabelle/jEdit / File Browser / Favorites to get there).

    For historic reasons, there might be some init_component line in $ISABELLE_HOME_USER/etc/settings --- these should be removed, to avoid duplicate component initialization.

  • Compile it:

• Patching the Isabelle/HOL library

  A few Isabelle/HOL files need to be modified so that exported proofs are of smaller size and that no oracle are used. See the modifications in HOL.patch. For now, HOL and HOL-Library are patched.

  • You may want to start with changing the permission on the HOL folder:

  chmod -R +w <path to your Isabelle distribution>/src/HOL/
  

  • Patch the folder, from the isabelle_dedukti folder:

  patch -up0 -d <path to your Isabelle distribution>/src/HOL/ < HOL.patch
  

  • To reverse the patch:

  patch -uREp0 -d <path to your Isabelle distribution>/src/HOL/ < HOL.patch
  

  • To update the patch:

  cd path_to_unpatched_Isabelle_dir
  diff -urNx '*~' -x '*.orig' . path_to_patched_Isabelle_dir/src/HOL > HOL.patch
  

• Deleting the Isabelle databases

  If something goes wrong, you may delete the databases (which means the proof terms will be rebuilt anew) located somewhere like:

  $ISABELLE_HOME_USER/Isabelle2023/heaps/polyml-<something>/log/
  

How to make Isabelle record proofs?

Isabelle theories are built within sessions, and sessions are defined in files named ROOT. A quick way to specify a ROOT file to Isabelle is the -d option.

To export proofs from Isabelle so that they can be translated to Dedukti or Lambdapi afterwards, users need to add the following options to the definition of the session:

export_theory,export_proofs,record_proofs=2

For instance, the following session builds the session HOL with proof recording:

session HOL_wp in HOL_wp = Pure +
  options [strict_facts,export_theory,export_proofs,record_proofs=2]
  sessions Tools HOL
  theories
    Main
    Complex_Main
  document_theories
    Tools.Code_Generator

Isabelle requires a dedicated directory for each session, specified by the in HOL_wp part above. Usually, it suffices to have an empty directory with the same name as the session.

To actually export proof terms from Isabelle, assuming the ROOT file containing the session info is located in $rootdir do:

isabelle build -b -d $rootdir $session

Command to translate Isabelle proofs to Dedukti or Lambdapi

WARNING: the Lambdapi output is temporarily deactivated for it needs to be fixed.

Command to translate a session to Dedukti: isabelle dedukti_session -d $root_dir $session.

By default, it generates in ./dkcheck/:

• parent_$session.dk representing the parent session, which may contain proofs that do not belong to any theory of $session (see remark below),
• a dk file for each theory of $session,
• session_$session.dk representing the session, and
• dkcheck_$session.sh a shell script to check all the generated dk files.

Run isabelle $command with no argument for more details.

Several sessions with proof exports are already defined in examples/ROOT. For each one, and the pre-defined session Pure, you should run the following commands in the order of dependencies between sessions (starting from Pure):

cd examples/
isabelle build -b -d. $session # generates the database of proofs
isabelle dedukti_session -d. $session # generates the lambdapi and dedukti proofs
bash ./dkcheck/dkcheck_$session.sh

To translate other sessions, follow these steps:

• add the relevant components to isabelle (for example, AFP),
• define the session:
  • specify the proof export options in your ROOT file;
  • make sure that the parent session also exports proofs (otherwise, Isabelle generates unfinished proofs which cannot be translated to Dedukti);
• run the commands of the previous section.

Remark: to visualize theory dependencies in HOL, you can look at the dependency graph of the HOL session.

Remark: In a database associated with a given theory, there might be proofs labelled from another theory. Fix: those proofs are not too many so they are just translated in this theory. This is a problem from Isabelle itself, and the reason is still unclear. One possible reason is the following: to check that a statement is really provable, Isabelle uses statements that has already be proven, possibly from other theories and sessions. Those proofs are "lifted", in the sense that they are tagged as belonging to the current theory, and they are possibly rewritten. Then, those proofs are given an identifier: if they are detected as a proof that already exists, they are given the already existing identifier and are not added to the database, otherwise they receive a fresh identifier and are added to the database. At this stage, some proofs that should already exist are given a fresh identifier and are added to the database, which creates a lot of duplication of proofs and costs time and memory.

Performance

Performance on a machine with 32 processors i9-13950HX and 64 Go RAM:

Project structure

• ast.scala provides an AST common to Dedukti and Lambdapi (it is strict subset of these languages)
• translate.scala translates Isabelle/Pure to the common Dedukti and Lambdapi AST
• writers.scala writes out an AST to either Dedukti or Lambdapi code
• exporter.scala provides the isabelle command dedukti_theory
• generator.scala provides the Isabelle command dedukti_session
• rootfile.scala provides the Isabelle command dedukti_root
• dkcheck.scala provides the Isabelle command dedukti_check

Browsing and modifying Isabelle sources

Without proper IDE support Isabelle sources may be very hard to read and write.

• Isabelle/ML: use Isabelle/jEdit and open ML files (with their proper .thy file opened as well), but for Isabelle/Pure a special bootstrap theory context is provided by $ISABELLE_HOME/src/Pure/ROOT.ML (see Documentation panel).

• Isabelle/HOL: use Isabelle/Pure to process the theory and ML sources in Isabelle/jEdit, e.g. like this:

  then open $ISABELLE_HOME/src/HOL/Main.thy via File Browser / Favorites

• Isabelle/Scala: use IntelliJ IDEA with the Java/Scala project generated by isabelle scala_project -L -f:

  idea "$(isabelle getenv -b ISABELLE_HOME_USER)/scala_project"