(* Authors: Gerwin Klein and Rafal Kolanski, 2012

   Maintainers: Gerwin Klein <kleing at cse.unsw.edu.au>

                Rafal Kolanski <rafal.kolanski at nicta.com.au>

*)

header "Separation Logic Tactics"

theory Sep_Tactics

begin

text {* A number of proof methods to assist with reasoning about separation logic. *}

section {* Selection (move-to-front) tactics *}

method_setup sep_select = {*

*} "Select nth separation conjunct in conclusion"

method_setup sep_select_asm = {*

*} "Select nth separation conjunct in assumptions"

section {* Substitution *}

method_setup "sep_subst" = {*

*}

"single-step substitution after solving one separation logic assumption"

section {* Forward Reasoning *}

method_setup "sep_drule" = {*

*} "drule after separating conjunction reordering"

method_setup "sep_frule" = {*

*} "frule after separating conjunction reordering"

section {* Backward Reasoning *}

method_setup "sep_rule" = {*

*} "applies rule after separating conjunction reordering"

section {* Cancellation of Common Conjuncts via Elimination Rules *}

ML {*

  structure SepCancel_Rules = Named_Thms (

    val name = @{binding "sep_cancel"};

    val description = "sep_cancel rules";

  );

*}

setup SepCancel_Rules.setup

text {*

  The basic @{text sep_cancel_tac} is minimal. It only eliminates

  erule-derivable conjuncts between an assumption and the conclusion.

  To have a more useful tactic, we augment it with more logic, to proceed as

  follows:

  \begin{itemize}

  \item try discharge the goal first using @{text tac}

  \item if that fails, invoke @{text sep_cancel_tac}

  \item if @{text sep_cancel_tac} succeeds

    \begin{itemize}

    \item try to finish off with tac (but ok if that fails)

    \item try to finish off with @{term sep_true} (but ok if that fails)

    \end{itemize}

  \end{itemize}

  *}

ML {*

  fun sep_cancel_smart_tac ctxt tac =

    let fun TRY' tac = tac ORELSE' (K all_tac)

    in

      tac

      ORELSE' (sep_cancel_tac ctxt tac

               THEN' TRY' tac

               THEN' TRY' (rtac @{thm TrueI}))

      ORELSE' (etac @{thm sep_conj_sep_emptyE}

               THEN' sep_cancel_tac ctxt tac

               THEN' TRY' tac

               THEN' TRY' (rtac @{thm TrueI}))

    end;

  fun sep_cancel_smart_tac_rules ctxt etacs =

      sep_cancel_smart_tac ctxt (FIRST' ([atac] @ etacs));

    let

      val etacs = map etac (SepCancel_Rules.get ctxt);

    in

      SIMPLE_METHOD' (sep_cancel_smart_tac_rules ctxt etacs)

*} "Separating conjunction conjunct cancellation"

text {*

  As above, but use blast with a depth limit to figure out where cancellation

  can be done. *}

    let

      val rules = SepCancel_Rules.get ctxt;

      val tac = Blast.depth_tac (ctxt addIs rules) 10;

    in

      SIMPLE_METHOD' (sep_cancel_smart_tac ctxt tac)

*} "Separating conjunction conjunct cancellation using blast"

end