signature SUB_PROBLEM =

 sig

   val tac_from_prog: Ctree.state -> term -> Tactic.input * Tactic.T

   val common_sub_thy: theory * theory -> theory

 end

 (**)

 structure Sub_Problem(**): SUB_PROBLEM(**) =

 struct

 (**)

 fun common_sub_thy (thy1, thy2) =

   if Context.subthy (thy1, thy2) then thy2

   else if Context.subthy (thy2, thy1) then thy1

     else Know_Store.get_ref_last_thy ()

 fun tac_from_prog (pt, _) (stac as Const (\<^const_name>\<open>Prog_Tac.SubProblem\<close>, _) $ spec' $ ags') =

     let

       val (dI, pI, mI) = Prog_Tac.dest_spec spec'

       val thy = common_sub_thy (Know_Store.get_via_last_thy dI, Ctree.root_thy pt);

       val init_ctxt = Proof_Context.init_global thy

 	    val ags = TermC.isalist2list ags';

 	    val (pI, pors, mI) = 

 	      if mI = ["no_met"]

 	      then

           let

             val pors = (M_Match.arguments thy ((#model o (Problem.from_store init_ctxt)) pI) ags): O_Model.T

 		          handle ERROR "actual args do not match formal args"

 			          => (M_Match.arguments_msg init_ctxt pI stac ags (*raise exn*);[]);

 		        val pI' = Refine.by_o_model' init_ctxt pors pI;

 		      in (pI', pors (* refinement over models with diff.precond only *), 

 		          (hd o #solve_mets o Problem.from_store init_ctxt) pI') end

 	      else (pI, (M_Match.arguments thy ((#model o Problem.from_store init_ctxt) pI) ags)

 		      handle ERROR "actual args do not match formal args"

 		      => (M_Match.arguments_msg init_ctxt pI stac ags(*raise exn*); []), mI);

       val (fmz_, vals) = O_Model.values' init_ctxt pors;

 	    val {cas, model, thy, ...} = Problem.from_store init_ctxt pI

 	    val dI = Context.theory_name thy (*take dI from _refined_ pbl*)

 	    val dI = Context.theory_name

         (common_sub_thy (Know_Store.get_via_last_thy dI, Ctree.root_thy pt))

 	    val ctxt = ContextC.init_for_prog init_ctxt vals

 	    val hdl =

         case cas of

 		      NONE => Auto_Prog.pblterm dI pI

 		    | SOME t => subst_atomic ((Model_Pattern.variables model) ~~~ vals) t

       val f = Auto_Prog.subpbl (ThmC.cut_longid dI) pI

     in

       (Tactic.Subproblem (dI, pI),	Tactic.Subproblem' ((dI, pI, mI), pors, hdl, fmz_, ctxt, f))

     end

   | tac_from_prog _ t =

     raise ERROR ("Sub_Problem.tac_from_prog not impl. for " ^ UnparseC.term (ContextC.for_ERROR ()) t)

 (**)end(**)