theory UF_Rec
imports Recs Hoare_tm
begin
section {* Coding of Turing Machines and Tapes*}
fun actnum :: "taction \<Rightarrow> nat"
where
"actnum W0 = 0"
| "actnum W1 = 1"
| "actnum L = 2"
| "actnum R = 3"
fun cellnum :: "Block \<Rightarrow> nat" where
"cellnum Bk = 0"
| "cellnum Oc = 1"
(* NEED TO CODE TAPES *)
text {* Coding tapes *}
fun code_tp :: "cell list \<Rightarrow> nat list"
where
"code_tp [] = []"
| "code_tp (c # tp) = (cellnum c) # code_tp tp"
fun Code_tp where
"Code_tp tp = lenc (code_tp tp)"
lemma code_tp_append [simp]:
"code_tp (tp1 @ tp2) = code_tp tp1 @ code_tp tp2"
by(induct tp1) (simp_all)
lemma code_tp_length [simp]:
"length (code_tp tp) = length tp"
by (induct tp) (simp_all)
lemma code_tp_nth [simp]:
"n < length tp \<Longrightarrow> (code_tp tp) ! n = cellnum (tp ! n)"
apply(induct n arbitrary: tp)
apply(simp_all)
apply(case_tac [!] tp)
apply(simp_all)
done
lemma code_tp_replicate [simp]:
"code_tp (c \<up> n) = (cellnum c) \<up> n"
by(induct n) (simp_all)
text {* Coding Configurations and TMs *}
fun Code_conf where
"Code_conf (s, l, r) = (s, Code_tp l, Code_tp r)"
fun code_instr :: "instr \<Rightarrow> nat" where
"code_instr i = penc (actnum (fst i)) (snd i)"
fun Code_instr :: "instr \<times> instr \<Rightarrow> nat" where
"Code_instr i = penc (code_instr (fst i)) (code_instr (snd i))"
fun code_tprog :: "tprog \<Rightarrow> nat list"
where
"code_tprog [] = []"
| "code_tprog (i # tm) = Code_instr i # code_tprog tm"
lemma code_tprog_length [simp]:
"length (code_tprog tp) = length tp"
by (induct tp) (simp_all)
lemma code_tprog_nth [simp]:
"n < length tp \<Longrightarrow> (code_tprog tp) ! n = Code_instr (tp ! n)"
by (induct tp arbitrary: n) (simp_all add: nth_Cons')
fun Code_tprog :: "tprog \<Rightarrow> nat"
where
"Code_tprog tm = lenc (code_tprog tm)"
section {* An Universal Function in HOL *}
text {* Reading and writing the encoded tape *}
fun Read where
"Read tp = ldec tp 0"
fun Write where
"Write n tp = penc (Suc n) (pdec2 tp)"
text {*
The @{text Newleft} and @{text Newright} functions on page 91 of B book.
They calculate the new left and right tape (@{text p} and @{text r})
according to an action @{text a}. Adapted to our encoding functions.
*}
fun Newleft :: "nat \<Rightarrow> nat \<Rightarrow> nat \<Rightarrow> nat"
where
"Newleft l r a = (if a = 0 then l else
if a = 1 then l else
if a = 2 then pdec2 l else
if a = 3 then penc (Suc (Read r)) l
else l)"
fun Newright :: "nat \<Rightarrow> nat \<Rightarrow> nat \<Rightarrow> nat"
where
"Newright l r a = (if a = 0 then Write 0 r
else if a = 1 then Write 1 r
else if a = 2 then penc (Suc (Read l)) r
else if a = 3 then pdec2 r
else r)"
text {*
The @{text "Action"} function given on page 92 of B book, which is used to
fetch Turing Machine intructions. In @{text "Action m q r"}, @{text "m"} is
the code of the Turing Machine, @{text "q"} is the current state of
Turing Machine, and @{text "r"} is the scanned cell of is the right tape.
*}
fun Actn :: "nat \<Rightarrow> nat \<Rightarrow> nat" where
"Actn n 0 = pdec1 (pdec1 n)"
| "Actn n _ = pdec1 (pdec2 n)"
fun Action :: "nat \<Rightarrow> nat \<Rightarrow> nat \<Rightarrow> nat"
where
"Action m q c = (if q \<noteq> 0 \<and> within m (q - 1) then Actn (ldec m (q - 1)) c else 4)"
fun Newstat :: "nat \<Rightarrow> nat \<Rightarrow> nat" where
"Newstat n 0 = pdec2 (pdec1 n)"
| "Newstat n _ = pdec2 (pdec2 n)"
fun Newstate :: "nat \<Rightarrow> nat \<Rightarrow> nat \<Rightarrow> nat"
where
"Newstate m q r = (if q \<noteq> 0 then Newstat (ldec m (q - 1)) r else 0)"
fun Conf :: "nat \<times> (nat \<times> nat) \<Rightarrow> nat"
where
"Conf (q, l, r) = lenc [q, l, r]"
fun State where
"State cf = ldec cf 0"
fun Left where
"Left cf = ldec cf 1"
fun Right where
"Right cf = ldec cf 2"
text {*
@{text "Steps cf m k"} computes the TM configuration after @{text "k"} steps of
execution of TM coded as @{text "m"}. @{text Step} is a single step of the TM.
*}
fun Step :: "nat \<Rightarrow> nat \<Rightarrow> nat"
where
"Step cf m = Conf (Newstate m (State cf) (Read (Right cf)),
Newleft (Left cf) (Right cf) (Action m (State cf) (Read (Right cf))),
Newright (Left cf) (Right cf) (Action m (State cf) (Read (Right cf))))"
fun Steps :: "nat \<Rightarrow> nat \<Rightarrow> nat \<Rightarrow> nat"
where
"Steps cf p 0 = cf"
| "Steps cf p (Suc n) = Steps (Step cf p) p n"
lemma Step_Steps_comm:
"Step (Steps cf p n) p = Steps (Step cf p) p n"
by (induct n arbitrary: cf) (simp_all only: Steps.simps)
text {* Decoding tapes back into numbers. *}
definition Stknum :: "nat \<Rightarrow> nat"
where
"Stknum z \<equiv> (\<Sum>i < enclen z. ldec z i)"
lemma Stknum_append:
"Stknum (Code_tp (tp1 @ tp2)) = Stknum (Code_tp tp1) + Stknum (Code_tp tp2)"
apply(simp only: Code_tp.simps)
apply(simp only: code_tp_append)
apply(simp only: Stknum_def)
apply(simp only: enclen_length length_append code_tp_length)
apply(simp only: list_encode_inverse)
apply(simp only: enclen_length length_append code_tp_length)
apply(simp)
apply(subgoal_tac "{..<length tp1 + length tp2} = {..<length tp1} \<union> {length tp1 ..<length tp1 + length tp2}")
prefer 2
apply(auto)[1]
apply(simp only:)
apply(subst setsum_Un_disjoint)
apply(auto)[2]
apply (metis ivl_disj_int_one(2))
apply(simp add: nth_append)
apply(subgoal_tac "{length tp1..<length tp1 + length tp2} = (\<lambda>x. x + length tp1) ` {0..<length tp2}")
prefer 2
apply(simp only: image_add_atLeastLessThan)
apply (metis comm_monoid_add_class.add.left_neutral nat_add_commute)
apply(simp only:)
apply(subst setsum_reindex)
prefer 2
apply(simp add: comp_def)
apply (metis atLeast0LessThan)
apply(simp add: inj_on_def)
done
lemma Stknum_up:
"Stknum (lenc (a \<up> n)) = n * a"
apply(induct n)
apply(simp_all add: Stknum_def list_encode_inverse del: replicate.simps)
done
lemma result:
"Stknum (Code_tp (<n> @ Bk \<up> l)) - 1 = n"
apply(simp only: Stknum_append)
apply(simp only: tape_of_nat.simps)
apply(simp only: Code_tp.simps)
apply(simp only: code_tp_replicate)
apply(simp only: cellnum.simps)
apply(simp only: Stknum_up)
apply(simp)
done
section {* Standard Tapes *}
definition
"right_std z \<equiv> (\<exists>i \<le> enclen z. 1 \<le> i \<and> (\<forall>j < i. ldec z j = 1) \<and> (\<forall>j < enclen z - i. ldec z (i + j) = 0))"
definition
"left_std z \<equiv> (\<forall>j < enclen z. ldec z j = 0)"
lemma ww:
"(\<exists>k l. 1 \<le> k \<and> tp = Oc \<up> k @ Bk \<up> l) \<longleftrightarrow>
(\<exists>i\<le>length tp. 1 \<le> i \<and> (\<forall>j < i. tp ! j = Oc) \<and> (\<forall>j < length tp - i. tp ! (i + j) = Bk))"
apply(rule iffI)
apply(erule exE)+
apply(simp)
apply(rule_tac x="k" in exI)
apply(auto)[1]
apply(simp add: nth_append)
apply(simp add: nth_append)
apply(erule exE)
apply(rule_tac x="i" in exI)
apply(rule_tac x="length tp - i" in exI)
apply(auto)
apply(rule sym)
apply(subst append_eq_conv_conj)
apply(simp)
apply(rule conjI)
apply (smt length_replicate length_take nth_equalityI nth_replicate nth_take)
by (smt length_drop length_replicate nth_drop nth_equalityI nth_replicate)
lemma right_std:
"(\<exists>k l. 1 \<le> k \<and> tp = Oc \<up> k @ Bk \<up> l) \<longleftrightarrow> right_std (Code_tp tp)"
apply(simp only: ww)
apply(simp add: right_std_def)
apply(simp only: list_encode_inverse)
apply(simp)
apply(auto)
apply(rule_tac x="i" in exI)
apply(simp)
apply(rule conjI)
apply (metis Suc_eq_plus1 Suc_neq_Zero cellnum.cases cellnum.simps(1) leD less_trans linorder_neqE_nat)
apply(auto)
by (metis One_nat_def cellnum.cases cellnum.simps(2) less_diff_conv n_not_Suc_n nat_add_commute)
lemma left_std:
"(\<exists>k. tp = Bk \<up> k) \<longleftrightarrow> left_std (Code_tp tp)"
apply(simp add: left_std_def)
apply(simp only: list_encode_inverse)
apply(simp)
apply(auto)
apply(rule_tac x="length tp" in exI)
apply(induct tp)
apply(simp)
apply(simp)
apply(auto)
apply(case_tac a)
apply(auto)
apply(case_tac a)
apply(auto)
by (metis Suc_less_eq nth_Cons_Suc)
section {* Standard- and Final Configurations, the Universal Function *}
text {*
@{text "Std cf"} returns true, if the configuration @{text "cf"}
is a stardard tape.
*}
fun Std :: "nat \<Rightarrow> bool"
where
"Std cf = (left_std (Left cf) \<and> right_std (Right cf))"
text{*
@{text "Stop m cf k"} means that afer @{text k} steps of
execution the TM coded by @{text m} and started in configuration
@{text cf} is in a stardard final configuration. *}
fun Final :: "nat \<Rightarrow> bool"
where
"Final cf = (State cf = 0)"
fun Stop :: "nat \<Rightarrow> nat \<Rightarrow> nat \<Rightarrow> bool"
where
"Stop m cf k = (Final (Steps cf m k) \<and> Std (Steps cf m k))"
text{*
@{text "Halt"} is the function calculating the steps a TM needs to
execute before reaching a stardard final configuration. This recursive
function is the only one that uses unbounded minimization. So it is the
only non-primitive recursive function needs to be used in the construction
of the universal function @{text "UF"}.
*}
fun Halt :: "nat \<Rightarrow> nat \<Rightarrow> nat"
where
"Halt m cf = (LEAST k. Stop m cf k)"
fun UF :: "nat \<Rightarrow> nat \<Rightarrow> nat"
where
"UF m cf = Stknum (Right (Steps cf m (Halt m cf))) - 1"
section {* The UF simulates Turing machines *}
lemma Update_left_simulate:
shows "Newleft (Code_tp l) (Code_tp r) (actnum a) = Code_tp (fst (update a (l, r)))"
apply(induct a)
apply(simp_all)
apply(case_tac l)
apply(simp_all)
apply(case_tac r)
apply(simp_all)
done
lemma Update_right_simulate:
shows "Newright (Code_tp l) (Code_tp r) (actnum a) = Code_tp (snd (update a (l, r)))"
apply(induct a)
apply(simp_all)
apply(case_tac r)
apply(simp_all)
apply(case_tac r)
apply(simp_all)
apply(case_tac l)
apply(simp_all)
apply(case_tac r)
apply(simp_all)
done
lemma Fetch_state_simulate:
"tm_wf tp \<Longrightarrow> Newstate (Code_tprog tp) st (cellnum c) = snd (fetch tp st c)"
apply(induct tp st c rule: fetch.induct)
apply(simp_all add: list_encode_inverse split: cell.split)
done
lemma Fetch_action_simulate:
"tm_wf tp \<Longrightarrow> Action (Code_tprog tp) st (cellnum c) = actnum (fst (fetch tp st c))"
apply(induct tp st c rule: fetch.induct)
apply(simp_all add: list_encode_inverse split: cell.split)
done
lemma Read_simulate:
"Read (Code_tp tp) = cellnum (read tp)"
apply(case_tac tp)
apply(simp_all)
done
lemma misc:
"2 < (3::nat)"
"1 < (3::nat)"
"0 < (3::nat)"
"length [x] = 1"
"length [x, y] = 2"
"length [x, y , z] = 3"
"[x, y, z] ! 0 = x"
"[x, y, z] ! 1 = y"
"[x, y, z] ! 2 = z"
apply(simp_all)
done
lemma Step_simulate:
assumes "tm_wf tp"
shows "Step (Conf (Code_conf (st, l, r))) (Code_tprog tp) = Conf (Code_conf (step (st, l, r) tp))"
apply(subst step.simps)
apply(simp only: Let_def)
apply(subst Step.simps)
apply(simp only: Conf.simps Code_conf.simps Right.simps Left.simps)
apply(simp only: list_encode_inverse)
apply(simp only: misc if_True Code_tp.simps)
apply(simp only: prod_case_beta)
apply(subst Fetch_state_simulate[OF assms, symmetric])
apply(simp only: State.simps)
apply(simp only: list_encode_inverse)
apply(simp only: misc if_True)
apply(simp only: Read_simulate[simplified Code_tp.simps])
apply(simp only: Fetch_action_simulate[OF assms])
apply(simp only: Update_left_simulate[simplified Code_tp.simps])
apply(simp only: Update_right_simulate[simplified Code_tp.simps])
apply(case_tac "update (fst (fetch tp st (read r))) (l, r)")
apply(simp only: Code_conf.simps)
apply(simp only: Conf.simps)
apply(simp)
done
lemma Steps_simulate:
assumes "tm_wf tp"
shows "Steps (Conf (Code_conf cf)) (Code_tprog tp) n = Conf (Code_conf (steps cf tp n))"
apply(induct n arbitrary: cf)
apply(simp)
apply(simp only: Steps.simps steps.simps)
apply(case_tac cf)
apply(simp only: )
apply(subst Step_simulate)
apply(rule assms)
apply(drule_tac x="step (a, b, c) tp" in meta_spec)
apply(simp)
done
lemma Final_simulate:
"Final (Conf (Code_conf cf)) = is_final cf"
by (case_tac cf) (simp)
lemma Std_simulate:
"Std (Conf (Code_conf cf)) = std_tape cf"
apply(case_tac cf)
apply(simp only: std_tape_def)
apply(simp only: Code_conf.simps)
apply(simp only: Conf.simps)
apply(simp only: Std.simps)
apply(simp only: Left.simps Right.simps)
apply(simp only: list_encode_inverse)
apply(simp only: misc if_True)
apply(simp only: left_std[symmetric] right_std[symmetric])
apply(simp)
by (metis Suc_le_D Suc_neq_Zero append_Cons nat.exhaust not_less_eq_eq replicate_Suc)
lemma UF_simulate:
assumes "tm_wf tm"
shows "UF (Code_tprog tm) (Conf (Code_conf cf)) =
Stknum (Right (Conf
(Code_conf (steps cf tm (LEAST n. is_final (steps cf tm n) \<and> std_tape (steps cf tm n)))))) - 1"
apply(simp only: UF.simps)
apply(subst Steps_simulate[symmetric, OF assms])
apply(subst Final_simulate[symmetric])
apply(subst Std_simulate[symmetric])
apply(simp only: Halt.simps)
apply(simp only: Steps_simulate[symmetric, OF assms])
apply(simp only: Stop.simps[symmetric])
done
section {* Universal Function as Recursive Functions *}
definition
"rec_read = CN rec_ldec [Id 1 0, constn 0]"
definition
"rec_write = CN rec_penc [CN S [Id 2 0], CN rec_pdec2 [Id 2 1]]"
definition
"rec_newleft =
(let cond0 = CN rec_eq [Id 3 2, constn 0] in
let cond1 = CN rec_eq [Id 3 2, constn 1] in
let cond2 = CN rec_eq [Id 3 2, constn 2] in
let cond3 = CN rec_eq [Id 3 2, constn 3] in
let case3 = CN rec_penc [CN S [CN rec_read [Id 3 1]], Id 3 0] in
CN rec_if [cond0, Id 3 0,
CN rec_if [cond1, Id 3 0,
CN rec_if [cond2, CN rec_pdec2 [Id 3 0],
CN rec_if [cond3, case3, Id 3 0]]]])"
definition
"rec_newright =
(let cond0 = CN rec_eq [Id 3 2, constn 0] in
let cond1 = CN rec_eq [Id 3 2, constn 1] in
let cond2 = CN rec_eq [Id 3 2, constn 2] in
let cond3 = CN rec_eq [Id 3 2, constn 3] in
let case2 = CN rec_penc [CN S [CN rec_read [Id 3 0]], Id 3 1] in
CN rec_if [cond0, CN rec_write [constn 0, Id 3 1],
CN rec_if [cond1, CN rec_write [constn 1, Id 3 1],
CN rec_if [cond2, case2,
CN rec_if [cond3, CN rec_pdec2 [Id 3 1], Id 3 1]]]])"
definition
"rec_actn = rec_swap (PR (CN rec_pdec1 [CN rec_pdec1 [Id 1 0]])
(CN rec_pdec1 [CN rec_pdec2 [Id 3 2]]))"
definition
"rec_action = (let cond1 = CN rec_noteq [Id 3 1, Z] in
let cond2 = CN rec_within [Id 3 0, CN rec_pred [Id 3 1]] in
let if_branch = CN rec_actn [CN rec_ldec [Id 3 0, CN rec_pred [Id 3 1]], Id 3 2]
in CN rec_if [CN rec_conj [cond1, cond2], if_branch, constn 4])"
definition
"rec_newstat = rec_swap (PR (CN rec_pdec2 [CN rec_pdec1 [Id 1 0]])
(CN rec_pdec2 [CN rec_pdec2 [Id 3 2]]))"
definition
"rec_newstate = (let cond = CN rec_noteq [Id 3 1, Z] in
let if_branch = CN rec_newstat [CN rec_ldec [Id 3 0, CN rec_pred [Id 3 1]], Id 3 2]
in CN rec_if [cond, if_branch, Z])"
definition
"rec_conf = rec_lenc [Id 3 0, Id 3 1, Id 3 2]"
definition
"rec_state = CN rec_ldec [Id 1 0, Z]"
definition
"rec_left = CN rec_ldec [Id 1 0, constn 1]"
definition
"rec_right = CN rec_ldec [Id 1 0, constn 2]"
definition
"rec_step = (let left = CN rec_left [Id 2 0] in
let right = CN rec_right [Id 2 0] in
let state = CN rec_state [Id 2 0] in
let read = CN rec_read [right] in
let action = CN rec_action [Id 2 1, state, read] in
let newstate = CN rec_newstate [Id 2 1, state, read] in
let newleft = CN rec_newleft [left, right, action] in
let newright = CN rec_newright [left, right, action]
in CN rec_conf [newstate, newleft, newright])"
definition
"rec_steps = PR (Id 2 0) (CN rec_step [Id 4 1, Id 4 3])"
definition
"rec_stknum = CN rec_minus
[CN (rec_sigma1 (CN rec_ldec [Id 2 1, Id 2 0])) [CN rec_enclen [Id 1 0], Id 1 0],
CN rec_ldec [Id 1 0, CN rec_enclen [Id 1 0]]]"
definition
"rec_right_std = (let bound = CN rec_enclen [Id 1 0] in
let cond1 = CN rec_le [CN (constn 1) [Id 2 0], Id 2 0] in
let cond2 = rec_all1_less (CN rec_eq [CN rec_ldec [Id 2 1, Id 2 0], constn 1]) in
let bound2 = CN rec_minus [CN rec_enclen [Id 2 1], Id 2 0] in
let cond3 = CN (rec_all2_less
(CN rec_eq [CN rec_ldec [Id 3 2, CN rec_add [Id 3 1, Id 3 0]], Z]))
[bound2, Id 2 0, Id 2 1] in
CN (rec_ex1 (CN rec_conj [CN rec_conj [cond1, cond2], cond3])) [bound, Id 1 0])"
definition
"rec_left_std = (let cond = CN rec_eq [CN rec_ldec [Id 2 1, Id 2 0], Z]
in CN (rec_all1_less cond) [CN rec_enclen [Id 1 0], Id 1 0])"
definition
"rec_std = CN rec_conj [CN rec_left_std [CN rec_left [Id 1 0]],
CN rec_right_std [CN rec_right [Id 1 0]]]"
definition
"rec_final = CN rec_eq [CN rec_state [Id 1 0], Z]"
definition
"rec_stop = (let steps = CN rec_steps [Id 3 2, Id 3 1, Id 3 0] in
CN rec_conj [CN rec_final [steps], CN rec_std [steps]])"
definition
"rec_halt = MN (CN rec_not [CN rec_stop [Id 3 1, Id 3 2, Id 3 0]])"
definition
"rec_uf = CN rec_pred
[CN rec_stknum
[CN rec_right
[CN rec_steps [CN rec_halt [Id 2 0, Id 2 1], Id 2 1, Id 2 0]]]]"
lemma read_lemma [simp]:
"rec_eval rec_read [x] = Read x"
by (simp add: rec_read_def)
lemma write_lemma [simp]:
"rec_eval rec_write [x, y] = Write x y"
by (simp add: rec_write_def)
lemma newleft_lemma [simp]:
"rec_eval rec_newleft [p, r, a] = Newleft p r a"
by (simp add: rec_newleft_def Let_def)
lemma newright_lemma [simp]:
"rec_eval rec_newright [p, r, a] = Newright p r a"
by (simp add: rec_newright_def Let_def)
lemma act_lemma [simp]:
"rec_eval rec_actn [n, c] = Actn n c"
apply(simp add: rec_actn_def)
apply(case_tac c)
apply(simp_all)
done
lemma action_lemma [simp]:
"rec_eval rec_action [m, q, c] = Action m q c"
by (simp add: rec_action_def)
lemma newstat_lemma [simp]:
"rec_eval rec_newstat [n, c] = Newstat n c"
apply(simp add: rec_newstat_def)
apply(case_tac c)
apply(simp_all)
done
lemma newstate_lemma [simp]:
"rec_eval rec_newstate [m, q, r] = Newstate m q r"
by (simp add: rec_newstate_def)
lemma conf_lemma [simp]:
"rec_eval rec_conf [q, l, r] = Conf (q, l, r)"
by(simp add: rec_conf_def)
lemma state_lemma [simp]:
"rec_eval rec_state [cf] = State cf"
by (simp add: rec_state_def)
lemma left_lemma [simp]:
"rec_eval rec_left [cf] = Left cf"
by (simp add: rec_left_def)
lemma right_lemma [simp]:
"rec_eval rec_right [cf] = Right cf"
by (simp add: rec_right_def)
lemma step_lemma [simp]:
"rec_eval rec_step [cf, m] = Step cf m"
by (simp add: Let_def rec_step_def)
lemma steps_lemma [simp]:
"rec_eval rec_steps [n, cf, p] = Steps cf p n"
by (induct n) (simp_all add: rec_steps_def Step_Steps_comm del: Step.simps)
lemma stknum_lemma [simp]:
"rec_eval rec_stknum [z] = Stknum z"
by (simp add: rec_stknum_def Stknum_def lessThan_Suc_atMost[symmetric])
lemma left_std_lemma [simp]:
"rec_eval rec_left_std [z] = (if left_std z then 1 else 0)"
by (simp add: Let_def rec_left_std_def left_std_def)
lemma right_std_lemma [simp]:
"rec_eval rec_right_std [z] = (if right_std z then 1 else 0)"
by (simp add: Let_def rec_right_std_def right_std_def)
lemma std_lemma [simp]:
"rec_eval rec_std [cf] = (if Std cf then 1 else 0)"
by (simp add: rec_std_def)
lemma final_lemma [simp]:
"rec_eval rec_final [cf] = (if Final cf then 1 else 0)"
by (simp add: rec_final_def)
lemma stop_lemma [simp]:
"rec_eval rec_stop [m, cf, k] = (if Stop m cf k then 1 else 0)"
by (simp add: Let_def rec_stop_def)
lemma halt_lemma [simp]:
"rec_eval rec_halt [m, cf] = Halt m cf"
by (simp add: rec_halt_def del: Stop.simps)
lemma uf_lemma [simp]:
"rec_eval rec_uf [m, cf] = UF m cf"
by (simp add: rec_uf_def)
(* value "size rec_uf" *)
end