converted IOA with curried function application
authorclasohm
Mon, 20 Mar 1995 15:37:03 +0100
changeset 966 3fd66f245ad7
parent 965 24eef3860714
child 967 bfcb53497a99
converted IOA with curried function application
src/HOL/IOA/ROOT.ML
src/HOL/IOA/meta_theory/Asig.ML
src/HOL/IOA/meta_theory/Asig.thy
src/HOL/IOA/meta_theory/IOA.ML
src/HOL/IOA/meta_theory/IOA.thy
src/HOL/IOA/meta_theory/Option.ML
src/HOL/IOA/meta_theory/Option.thy
src/HOL/IOA/meta_theory/Solve.ML
src/HOL/IOA/meta_theory/Solve.thy
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/IOA/ROOT.ML	Mon Mar 20 15:37:03 1995 +0100
@@ -0,0 +1,22 @@
+(*  Title:      HOL/IOA/ROOT.ML
+    ID:         $Id$
+    Author:     Tobias Nipkow & Konrad Slind
+    Copyright   1994  TU Muenchen
+
+This is the ROOT file for the theory of I/O-Automata.
+The formalization is by a semantic model of I/O-Automata.
+For details see
+
+@unpublished{Nipkow-Slind-IOA,
+author={Tobias Nipkow and Konrad Slind},
+title={{I/O} Automata in {Isabelle/HOL}},
+year=1994,
+note={Submitted for publication}}
+ftp://ftp.informatik.tu-muenchen.de/local/lehrstuhl/nipkow/ioa.ps.gz
+
+Should be executed in the subdirectory HOL.
+*)
+goals_limit := 1;
+
+loadpath := "IOA/meta_theory" :: "IOA/example" :: !loadpath;
+use_thy "Correctness"  handle _ => exit 1;
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/IOA/meta_theory/Asig.ML	Mon Mar 20 15:37:03 1995 +0100
@@ -0,0 +1,11 @@
+(*  Title:      HOL/IOA/meta_theory/Asig.ML
+    ID:         $Id$
+    Author:     Tobias Nipkow & Konrad Slind
+    Copyright   1994  TU Muenchen
+
+Action signatures
+*)
+
+open Asig;
+
+val asig_projections = [asig_inputs_def, asig_outputs_def, asig_internals_def];
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/IOA/meta_theory/Asig.thy	Mon Mar 20 15:37:03 1995 +0100
@@ -0,0 +1,45 @@
+(*  Title:      HOL/IOA/meta_theory/Asig.thy
+    ID:         $Id$
+    Author:     Tobias Nipkow & Konrad Slind
+    Copyright   1994  TU Muenchen
+
+Action signatures
+*)
+
+Asig = Option +
+
+types 
+
+'a signature = "('a set * 'a set * 'a set)"
+
+consts
+  actions,inputs,outputs,internals,externals
+                ::"'action signature => 'action set"
+  is_asig       ::"'action signature => bool"
+  mk_ext_asig   ::"'action signature => 'action signature"
+
+
+defs
+
+asig_inputs_def    "inputs == fst"
+asig_outputs_def   "outputs == (fst o snd)"
+asig_internals_def "internals == (snd o snd)"
+
+actions_def
+   "actions(asig) == (inputs(asig) Un outputs(asig) Un internals(asig))"
+
+externals_def
+   "externals(asig) == (inputs(asig) Un outputs(asig))"
+
+is_asig_def
+  "is_asig(triple) ==            \
+   \  ((inputs(triple) Int outputs(triple) = {})    & \
+   \   (outputs(triple) Int internals(triple) = {}) & \
+   \   (inputs(triple) Int internals(triple) = {}))"
+
+
+mk_ext_asig_def
+  "mk_ext_asig(triple) == <inputs(triple), outputs(triple), {}>"
+
+
+end 
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/IOA/meta_theory/IOA.ML	Mon Mar 20 15:37:03 1995 +0100
@@ -0,0 +1,151 @@
+(*  Title:      HOL/IOA/meta_theory/IOA.ML
+    ID:         $Id$
+    Author:     Tobias Nipkow & Konrad Slind
+    Copyright   1994  TU Muenchen
+
+The I/O automata of Lynch and Tuttle.
+*)
+
+open IOA Asig;
+
+val ioa_projections = [asig_of_def, starts_of_def, trans_of_def];
+
+val exec_rws = [executions_def,is_execution_fragment_def];
+
+goal IOA.thy
+"asig_of(<x,y,z>) = x & starts_of(<x,y,z>) = y & trans_of(<x,y,z>) = z";
+  by (simp_tac (SS addsimps ioa_projections) 1);
+  qed "ioa_triple_proj";
+
+goalw IOA.thy [ioa_def,state_trans_def,actions_def, is_asig_def]
+  "!!A. [| IOA(A); <s1,a,s2>:trans_of(A) |] ==> a:actions(asig_of(A))";
+  by (REPEAT(etac conjE 1));
+  by (EVERY1[etac allE, etac impE, atac]);
+  by (asm_full_simp_tac SS 1);
+qed "trans_in_actions";
+
+
+goal IOA.thy "filter_oseq p (filter_oseq p s) = filter_oseq p s";
+  by (simp_tac (SS addsimps [filter_oseq_def]) 1);
+  by (rtac ext 1);
+  by (Option.option.induct_tac "s(i)" 1);
+  by (simp_tac SS 1);
+  by (simp_tac (SS setloop (split_tac [expand_if])) 1);
+qed "filter_oseq_idemp";
+
+goalw IOA.thy [mk_behaviour_def,filter_oseq_def]
+"(mk_behaviour A s n = None) =                                        \
+\  (s(n)=None | (? a. s(n)=Some(a) & a ~: externals(asig_of(A))))     \
+\  &                                                                  \
+\  (mk_behaviour A s n = Some(a)) =                                   \
+\   (s(n)=Some(a) & a : externals(asig_of(A)))";
+  by (Option.option.induct_tac "s(n)" 1);
+  by (ALLGOALS (simp_tac (SS setloop (split_tac [expand_if]))));
+  by (fast_tac HOL_cs 1);
+qed "mk_behaviour_thm";
+
+goalw IOA.thy [reachable_def] "!!A. s:starts_of(A) ==> reachable A s";
+  by (res_inst_tac [("x","<%i.None,%i.s>")] bexI 1);
+  by (simp_tac SS 1);
+  by (asm_simp_tac (SS addsimps exec_rws) 1);
+qed "reachable_0";
+
+goalw IOA.thy (reachable_def::exec_rws)
+"!!A. [| reachable A s; <s,a,t> : trans_of(A) |] ==> reachable A t";
+  by(asm_full_simp_tac SS 1);
+  by(safe_tac set_cs);
+  by(res_inst_tac [("x","<%i.if i<n then fst ex i                    \
+\                            else (if i=n then Some a else None),    \
+\                         %i.if i<Suc n then snd ex i else t>")] bexI 1);
+  by(res_inst_tac [("x","Suc(n)")] exI 1);
+  by(simp_tac SS 1);
+  by(asm_simp_tac (SS delsimps [less_Suc_eq]) 1);
+  by(REPEAT(rtac allI 1));
+  by(res_inst_tac [("m","na"),("n","n")] (make_elim less_linear) 1);
+  be disjE 1;
+  by(asm_simp_tac SS 1);
+  be disjE 1;
+  by(asm_simp_tac SS 1);
+  by(fast_tac HOL_cs 1);
+  by(forward_tac [less_not_sym] 1);
+  by(asm_simp_tac (SS addsimps [less_not_refl2]) 1);
+qed "reachable_n";
+
+val [p1,p2] = goalw IOA.thy [invariant_def]
+  "[| !!s. s:starts_of(A) ==> P(s);                                          \
+\     !!s t a. [|reachable A s; P(s)|] ==> <s,a,t>: trans_of(A) --> P(t) |] \
+\  ==> invariant A P";
+  by (rewrite_goals_tac(reachable_def::Let_def::exec_rws));
+  by (safe_tac set_cs);
+  by (res_inst_tac [("Q","reachable A (snd ex n)")] conjunct1 1);
+  by (nat_ind_tac "n" 1);
+  by (fast_tac (set_cs addIs [p1,reachable_0]) 1);
+  by (eres_inst_tac[("x","n1")]allE 1);
+  by (eres_inst_tac[("P","%x.!a.?Q x a"), ("opt","fst ex n1")] optE 1);
+  by (asm_simp_tac HOL_ss 1);
+  by (safe_tac HOL_cs);
+  by (etac (p2 RS mp) 1);
+  by (ALLGOALS(fast_tac(set_cs addDs [hd Option.option.inject RS iffD1,
+                                      reachable_n])));
+qed "invariantI";
+
+val [p1,p2] = goal IOA.thy
+ "[| !!s. s : starts_of(A) ==> P(s); \
+\   !!s t a. reachable A s ==> P(s) --> <s,a,t>:trans_of(A) --> P(t) \
+\ |] ==> invariant A P";
+  by (fast_tac (HOL_cs addSIs [invariantI] addSDs [p1,p2]) 1);
+qed "invariantI1";
+
+val [p1,p2] = goalw IOA.thy [invariant_def]
+"[| invariant A P; reachable A s |] ==> P(s)";
+   br(p2 RS (p1 RS spec RS mp))1;
+qed "invariantE";
+
+goal IOA.thy 
+"actions(asig_comp a b) = actions(a) Un actions(b)";
+  by(simp_tac (prod_ss addsimps
+               ([actions_def,asig_comp_def]@asig_projections)) 1);
+  by(fast_tac eq_cs 1);
+qed "actions_asig_comp";
+
+goal IOA.thy
+"starts_of(A || B) = {p. fst(p):starts_of(A) & snd(p):starts_of(B)}";
+  by(simp_tac (SS addsimps (par_def::ioa_projections)) 1);
+qed "starts_of_par";
+
+(* Every state in an execution is reachable *)
+goalw IOA.thy [reachable_def] 
+"!!A. ex:executions(A) ==> !n. reachable A (snd ex n)";
+  by (fast_tac set_cs 1);
+qed "states_of_exec_reachable";
+
+
+goal IOA.thy 
+"<s,a,t> : trans_of(A || B || C || D) =                                      \
+\ ((a:actions(asig_of(A)) | a:actions(asig_of(B)) | a:actions(asig_of(C)) |  \
+\   a:actions(asig_of(D))) &                                                 \
+\  (if a:actions(asig_of(A)) then <fst(s),a,fst(t)>:trans_of(A)              \
+\   else fst t=fst s) &                                                      \
+\  (if a:actions(asig_of(B)) then <fst(snd(s)),a,fst(snd(t))>:trans_of(B)    \
+\   else fst(snd(t))=fst(snd(s))) &                                          \
+\  (if a:actions(asig_of(C)) then                                            \
+\     <fst(snd(snd(s))),a,fst(snd(snd(t)))>:trans_of(C)                      \
+\   else fst(snd(snd(t)))=fst(snd(snd(s)))) &                                \
+\  (if a:actions(asig_of(D)) then                                            \
+\     <snd(snd(snd(s))),a,snd(snd(snd(t)))>:trans_of(D)                      \
+\   else snd(snd(snd(t)))=snd(snd(snd(s)))))";
+  by(simp_tac (SS addsimps ([par_def,actions_asig_comp,Pair_fst_snd_eq]@
+                            ioa_projections)
+                  setloop (split_tac [expand_if])) 1);
+qed "trans_of_par4";
+
+goal IOA.thy "starts_of(restrict ioa acts) = starts_of(ioa) &     \
+\             trans_of(restrict ioa acts) = trans_of(ioa) &       \
+\             reachable (restrict ioa acts) s = reachable ioa s";
+by(simp_tac (SS addsimps ([is_execution_fragment_def,executions_def,
+                           reachable_def,restrict_def]@ioa_projections)) 1);
+qed "cancel_restrict";
+
+goal IOA.thy "asig_of(A || B) = asig_comp (asig_of A) (asig_of B)";
+  by(simp_tac (SS addsimps (par_def::ioa_projections)) 1);
+qed "asig_of_par";
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/IOA/meta_theory/IOA.thy	Mon Mar 20 15:37:03 1995 +0100
@@ -0,0 +1,186 @@
+(*  Title:      HOL/IOA/meta_theory/IOA.thy
+    ID:         $Id$
+    Author:     Tobias Nipkow & Konrad Slind
+    Copyright   1994  TU Muenchen
+
+The I/O automata of Lynch and Tuttle.
+*)
+
+IOA = Asig +
+
+types
+   'a seq            =   "nat => 'a"
+   'a oseq           =   "nat => 'a option"
+   ('a,'b)execution  =   "'a oseq * 'b seq"
+   ('a,'s)transition =   "('s * 'a * 's)"
+   ('a,'s)ioa        =   "'a signature * 's set * ('a,'s)transition set"
+
+consts
+
+  (* IO automata *)
+  state_trans::"['action signature, ('action,'state)transition set] => bool"
+  asig_of    ::"('action,'state)ioa => 'action signature"
+  starts_of  ::"('action,'state)ioa => 'state set"
+  trans_of   ::"('action,'state)ioa => ('action,'state)transition set"
+  IOA	     ::"('action,'state)ioa => bool"
+
+  (* Executions, schedules, and behaviours *)
+
+  is_execution_fragment,
+  has_execution ::"[('action,'state)ioa, ('action,'state)execution] => bool"
+  executions    :: "('action,'state)ioa => ('action,'state)execution set"
+  mk_behaviour  :: "[('action,'state)ioa, 'action oseq] => 'action oseq"
+  reachable     :: "[('action,'state)ioa, 'state] => bool"
+  invariant     :: "[('action,'state)ioa, 'state=>bool] => bool"
+  has_behaviour :: "[('action,'state)ioa, 'action oseq] => bool"
+  behaviours    :: "('action,'state)ioa => 'action oseq set"
+
+  (* Composition of action signatures and automata *)
+  compatible_asigs ::"('a => 'action signature) => bool"
+  asig_composition ::"('a => 'action signature) => 'action signature"
+  compatible_ioas  ::"('a => ('action,'state)ioa) => bool"
+  ioa_composition  ::"('a => ('action, 'state)ioa) =>('action,'a => 'state)ioa"
+
+  (* binary composition of action signatures and automata *)
+  compat_asigs ::"['action signature, 'action signature] => bool"
+  asig_comp    ::"['action signature, 'action signature] => 'action signature"
+  compat_ioas  ::"[('action,'state)ioa, ('action,'state)ioa] => bool"
+  "||"         ::"[('a,'s)ioa, ('a,'t)ioa] => ('a,'s*'t)ioa"  (infixr 10)
+
+  (* Filtering and hiding *)
+  filter_oseq  :: "('a => bool) => 'a oseq => 'a oseq"
+
+  restrict_asig :: "['a signature, 'a set] => 'a signature"
+  restrict      :: "[('a,'s)ioa, 'a set] => ('a,'s)ioa"
+
+  (* Notions of correctness *)
+  ioa_implements :: "[('action,'state1)ioa, ('action,'state2)ioa] => bool"
+
+
+defs
+
+state_trans_def
+  "state_trans asig R == \
+  \  (!triple. triple:R --> fst(snd(triple)):actions(asig)) & \
+  \  (!a. (a:inputs(asig)) --> (!s1. ? s2. <s1,a,s2>:R))"
+
+
+asig_of_def   "asig_of == fst"
+starts_of_def "starts_of == (fst o snd)"
+trans_of_def  "trans_of == (snd o snd)"
+
+ioa_def
+  "IOA(ioa) == (is_asig(asig_of(ioa))      &                            \
+  \             (~ starts_of(ioa) = {})    &                            \
+  \             state_trans (asig_of ioa) (trans_of ioa))"
+
+
+(* An execution fragment is modelled with a pair of sequences:
+ * the first is the action options, the second the state sequence.
+ * Finite executions have None actions from some point on.
+ *******)
+is_execution_fragment_def
+  "is_execution_fragment A ex ==                                        \
+  \  let act = fst(ex); state = snd(ex)                                 \
+  \  in !n a. (act(n)=None --> state(Suc(n)) = state(n)) &              \
+  \           (act(n)=Some(a) --> <state(n),a,state(Suc(n))>:trans_of(A))"
+
+
+executions_def
+  "executions(ioa) == {e. snd e 0:starts_of(ioa) &                      \
+\                        is_execution_fragment ioa e}"
+
+
+(* Is a state reachable. Using an inductive definition, this could be defined
+ * by the following 2 rules
+ *
+ *      x:starts_of(ioa)
+ *      ----------------
+ *      reachable(ioa,x)  
+ *
+ *      reachable(ioa,s) & ? <s,a,s'>:trans_of(ioa)
+ *      -------------------------------------------
+ *               reachable(ioa,s')
+ *
+ * A direkt definition follows.
+ *******************************)
+reachable_def
+  "reachable ioa s == (? ex:executions(ioa). ? n. (snd ex n) = s)"
+
+
+invariant_def "invariant A P == (!s. reachable A s --> P(s))"
+
+
+(* Restrict the trace to those members of the set s *)
+filter_oseq_def
+  "filter_oseq p s ==                                                   \
+\   (%i.case s(i)                                                       \
+\         of None => None                                               \
+\          | Some(x) => if p x then Some x else None)"
+
+
+mk_behaviour_def
+  "mk_behaviour(ioa) == filter_oseq(%a.a:externals(asig_of(ioa)))"
+
+
+(* Does an ioa have an execution with the given behaviour *)
+has_behaviour_def
+  "has_behaviour ioa b ==                                               \
+\     (? ex:executions(ioa). b = mk_behaviour ioa (fst ex))"
+
+
+(* All the behaviours of an ioa *)
+behaviours_def
+  "behaviours(ioa) == {b. has_behaviour ioa b}"
+
+
+compat_asigs_def
+  "compat_asigs a1 a2 ==                                                \
+ \ (((outputs(a1) Int outputs(a2)) = {}) &                              \
+ \  ((internals(a1) Int actions(a2)) = {}) &                            \
+ \  ((internals(a2) Int actions(a1)) = {}))"
+
+
+compat_ioas_def
+  "compat_ioas ioa1 ioa2 == compat_asigs (asig_of(ioa1)) (asig_of(ioa2))"
+
+
+asig_comp_def
+  "asig_comp a1 a2 ==                                                   \
+  \   (<(inputs(a1) Un inputs(a2)) - (outputs(a1) Un outputs(a2)),      \
+  \     (outputs(a1) Un outputs(a2)),                                   \
+  \     (internals(a1) Un internals(a2))>)"
+
+
+par_def
+  "(ioa1 || ioa2) ==                                                    \
+  \    <asig_comp (asig_of ioa1) (asig_of ioa2),                        \
+  \     {pr. fst(pr):starts_of(ioa1) & snd(pr):starts_of(ioa2)},        \
+  \     {tr. let s = fst(tr); a = fst(snd(tr)); t = snd(snd(tr))        \
+  \          in (a:actions(asig_of(ioa1)) | a:actions(asig_of(ioa2))) & \
+  \             (if a:actions(asig_of(ioa1)) then                       \
+  \                <fst(s),a,fst(t)>:trans_of(ioa1)                     \
+  \              else fst(t) = fst(s))                                  \
+  \             &                                                       \
+  \             (if a:actions(asig_of(ioa2)) then                       \
+  \                <snd(s),a,snd(t)>:trans_of(ioa2)                     \
+  \              else snd(t) = snd(s))}>"
+
+
+restrict_asig_def
+  "restrict_asig asig actns ==                                          \
+\    <inputs(asig) Int actns, outputs(asig) Int actns,                  \
+\     internals(asig) Un (externals(asig) - actns)>"
+
+
+restrict_def
+  "restrict ioa actns ==                                               \
+\    <restrict_asig (asig_of ioa) actns, starts_of(ioa), trans_of(ioa)>"
+
+
+ioa_implements_def
+  "ioa_implements ioa1 ioa2 ==        \
+\     (externals(asig_of(ioa1)) = externals(asig_of(ioa2)) & \
+\      behaviours(ioa1) <= behaviours(ioa2))"
+
+end 
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/IOA/meta_theory/Option.ML	Mon Mar 20 15:37:03 1995 +0100
@@ -0,0 +1,16 @@
+(*  Title:      Option.ML
+    ID:         $Id$
+    Author:     Tobias Nipkow
+    Copyright   1994  TU Muenchen
+
+Derived rules
+*)
+
+val option_rws = Let_def :: Option.option.simps;
+val SS = arith_ss addsimps option_rws;
+
+val [prem] = goal Option.thy "P(opt) ==> P(None) | (? x. P(Some(x)))";
+ br (prem RS rev_mp) 1;
+ by (Option.option.induct_tac "opt" 1);
+ by (ALLGOALS(fast_tac HOL_cs));
+val optE = store_thm("optE", standard(result() RS disjE));
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/IOA/meta_theory/Option.thy	Mon Mar 20 15:37:03 1995 +0100
@@ -0,0 +1,11 @@
+(*  Title:      Option.thy
+    ID:         $Id$
+    Author:     Tobias Nipkow
+    Copyright   1994  TU Muenchen
+
+Datatype 'a option
+*)
+
+Option = Arith +
+datatype 'a option = None | Some('a)
+end
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/IOA/meta_theory/Solve.ML	Mon Mar 20 15:37:03 1995 +0100
@@ -0,0 +1,45 @@
+(*  Title:      HOL/IOA/meta_theory/Solve.ML
+    ID:         $Id$
+    Author:     Tobias Nipkow & Konrad Slind
+    Copyright   1994  TU Muenchen
+
+Weak possibilities mapping (abstraction)
+*)
+
+open Solve;
+
+val SS = SS addsimps [mk_behaviour_thm,trans_in_actions];
+
+goalw Solve.thy [is_weak_pmap_def,behaviours_def]
+  "!!f. [| IOA(C); IOA(A); externals(asig_of(C)) = externals(asig_of(A)); \
+\          is_weak_pmap f C A |] ==> behaviours(C) <= behaviours(A)";
+
+  by (simp_tac(SS addsimps [has_behaviour_def])1);
+  by (safe_tac set_cs);
+
+  (* give execution of abstract automata *)
+  by (res_inst_tac[("x","<mk_behaviour A (fst ex),%i.f(snd ex i)>")] bexI 1);
+
+  (* Behaviours coincide *)
+  by (asm_simp_tac (SS addsimps [mk_behaviour_def,filter_oseq_idemp])1);
+
+  (* Use lemma *)
+  by (forward_tac [states_of_exec_reachable] 1);
+
+  (* Now show that it's an execution *)
+  by (asm_full_simp_tac(SS addsimps [executions_def]) 1);
+  by (safe_tac set_cs);
+
+  (* Start states map to start states *)
+  by (dtac bspec 1);
+  by (atac 1);
+
+  (* Show that it's an execution fragment *)
+  by (asm_full_simp_tac (SS addsimps [is_execution_fragment_def])1);
+  by (safe_tac HOL_cs);
+
+  by (eres_inst_tac [("x","snd ex n")] allE 1);
+  by (eres_inst_tac [("x","snd ex (Suc n)")] allE 1);
+  by (eres_inst_tac [("x","a")] allE 1);
+  by (asm_full_simp_tac SS 1);
+qed "trace_inclusion";
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/IOA/meta_theory/Solve.thy	Mon Mar 20 15:37:03 1995 +0100
@@ -0,0 +1,26 @@
+(*  Title:      HOL/IOA/meta_theory/Solve.thy
+    ID:         $Id$
+    Author:     Tobias Nipkow & Konrad Slind
+    Copyright   1994  TU Muenchen
+
+Weak possibilities mapping (abstraction)
+*)
+
+Solve = IOA +
+
+consts
+
+  is_weak_pmap :: "['c => 'a, ('action,'c)ioa,('action,'a)ioa] => bool"
+
+defs
+
+is_weak_pmap_def
+  "is_weak_pmap f C A ==                          \
+\   (!s:starts_of(C). f(s):starts_of(A)) &        \
+\   (!s t a. reachable C s &                      \
+\            <s,a,t>:trans_of(C)                  \
+\            --> (if a:externals(asig_of(C)) then \
+\                   <f(s),a,f(t)>:trans_of(A)     \
+\                 else f(s)=f(t)))"
+
+end