(*  Title:      Tools/Code/code_simp.ML

     Author:     Florian Haftmann, TU Muenchen

 Connecting the simplifier and the code generator.

 *)

 signature CODE_SIMP =

 sig

   val no_frees_conv: conv -> conv

   val map_ss: (simpset -> simpset) -> theory -> theory

   val dynamic_eval_conv: conv

   val dynamic_eval_tac: theory -> int -> tactic

   val dynamic_eval_value: theory -> term -> term

   val static_eval_conv: theory -> simpset option -> string list -> conv

   val static_eval_tac: theory -> simpset option -> string list -> int -> tactic

   val setup: theory -> theory

 end;

 structure Code_Simp : CODE_SIMP =

 struct

 (* avoid free variables during conversion *)

 fun no_frees_conv conv ct =

   let

     val frees = Thm.add_cterm_frees ct [];

     fun apply_beta free thm = Thm.combination thm (Thm.reflexive free)

       |> Conv.fconv_rule (Conv.arg_conv (Conv.try_conv (Thm.beta_conversion false)))

       |> Conv.fconv_rule (Conv.arg1_conv (Thm.beta_conversion false));

   in

     ct

     |> fold_rev Thm.cabs frees

     |> conv

     |> fold apply_beta frees

   end;

 (* dedicated simpset *)

 structure Simpset = Theory_Data

 (

   type T = simpset;

   val empty = empty_ss;

   fun extend ss = MetaSimplifier.inherit_context empty_ss ss;

   val merge = merge_ss;

 );

 val map_ss = Simpset.map;

 fun simpset_default thy = Simplifier.global_context thy o the_default (Simpset.get thy);

 (* build simpset and conversion from program *)

 fun add_stmt (Code_Thingol.Fun (_, ((_, eqs), some_cong))) ss =

       ss addsimps (map_filter (fst o snd)) eqs addcongs (the_list some_cong)

   | add_stmt (Code_Thingol.Classinst (_, (_, (classparam_instances, _)))) ss =

       ss addsimps (map (fst o snd) classparam_instances)

   | add_stmt _ ss = ss;

 val add_program = Graph.fold (add_stmt o fst o snd);

 fun rewrite_modulo thy some_ss program = Simplifier.full_rewrite

   (add_program program (simpset_default thy some_ss));

 fun conclude_tac thy some_ss = Simplifier.full_simp_tac (simpset_default thy some_ss);

 (* evaluation with dynamic code context *)

 val dynamic_eval_conv = Conv.tap_thy (fn thy => no_frees_conv (Code_Thingol.dynamic_eval_conv thy

   (fn naming => fn program => fn t => fn deps => rewrite_modulo thy NONE program)));

 fun dynamic_eval_tac thy = CONVERSION dynamic_eval_conv THEN' conclude_tac thy NONE;

 fun dynamic_eval_value thy = snd o Logic.dest_equals o Thm.prop_of o dynamic_eval_conv o Thm.cterm_of thy;

 val setup = Method.setup (Binding.name "code_simp")

   (Scan.succeed (SIMPLE_METHOD' o (CHANGED_PROP oo dynamic_eval_tac o ProofContext.theory_of)))

   "simplification with code equations"

   #> Value.add_evaluator ("simp", dynamic_eval_value o ProofContext.theory_of);

 (* evaluation with static code context *)

 fun static_eval_conv thy some_ss consts = no_frees_conv

   (Code_Thingol.static_eval_conv_simple thy consts

     (fn program => fn thy => fn _ => fn _ => rewrite_modulo thy some_ss program));

 fun static_eval_tac thy some_ss consts = CONVERSION (static_eval_conv thy some_ss consts)

   THEN' conclude_tac thy some_ss;

 end;