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-rw-r--r--pretyping/cbv.ml170
1 files changed, 91 insertions, 79 deletions
diff --git a/pretyping/cbv.ml b/pretyping/cbv.ml
index f4c612a5..8c03d0df 100644
--- a/pretyping/cbv.ml
+++ b/pretyping/cbv.ml
@@ -6,7 +6,7 @@
(* * GNU Lesser General Public License Version 2.1 *)
(************************************************************************)
-(* $Id: cbv.ml 11897 2009-02-09 19:28:02Z barras $ *)
+(* $Id$ *)
open Util
open Pp
@@ -27,7 +27,14 @@ open Esubst
* in normal form and neutral (i.e. not a lambda, a construct or a
* (co)fix, because they may produce redexes by applying them,
* or putting them in a case)
- * LAM(x,a,b,S) is the term [S]([x:a]b). the bindings is propagated
+ * STACK(k,v,stk) represents an irreductible value [v] in the stack [stk].
+ * [k] is a delayed shift to be applied to both the value and
+ * the stack.
+ * CBN(t,S) is the term [S]t. It is used to delay evaluation. For
+ * instance products are evaluated only when actually needed
+ * (CBN strategy).
+ * LAM(n,a,b,S) is the term [S]([x:a]b) where [a] is a list of bindings and
+ * [n] is the length of [a]. the environment [S] is propagated
* only when the abstraction is applied, and then we use the rule
* ([S]([x:a]b) c) --> [S.c]b
* This corresponds to the usual strategy of weak reduction
@@ -36,28 +43,47 @@ open Esubst
* weak reduction.
* CONSTR(c,args) is the constructor [c] applied to [args].
*
- * Note that any term has not an equivalent in cbv_value: for example,
- * a product (x:A)B must be in normal form because only VAL may
- * represent it, and the argument of VAL is always in normal
- * form. This remark precludes coding a head reduction with these
- * functions. Anyway, does it make sense to head reduce with a
- * call-by-value strategy ?
*)
type cbv_value =
| VAL of int * constr
+ | STACK of int * cbv_value * cbv_stack
+ | CBN of constr * cbv_value subs
| LAM of int * (name * constr) list * constr * cbv_value subs
| FIXP of fixpoint * cbv_value subs * cbv_value array
| COFIXP of cofixpoint * cbv_value subs * cbv_value array
| CONSTR of constructor * cbv_value array
+(* type of terms with a hole. This hole can appear only under App or Case.
+ * TOP means the term is considered without context
+ * APP(v,stk) means the term is applied to v, and then the context stk
+ * (v.0 is the first argument).
+ * this corresponds to the application stack of the KAM.
+ * The members of l are values: we evaluate arguments before
+ calling the function.
+ * CASE(t,br,pat,S,stk) means the term is in a case (which is himself in stk
+ * t is the type of the case and br are the branches, all of them under
+ * the subs S, pat is information on the patterns of the Case
+ * (Weak reduction: we propagate the sub only when the selected branch
+ * is determined)
+ *
+ * Important remark: the APPs should be collapsed:
+ * (APP (l,(APP ...))) forbidden
+ *)
+and cbv_stack =
+ | TOP
+ | APP of cbv_value array * cbv_stack
+ | CASE of constr * constr array * case_info * cbv_value subs * cbv_stack
+
(* les vars pourraient etre des constr,
- cela permet de retarder les lift: utile ?? *)
+ cela permet de retarder les lift: utile ?? *)
(* relocation of a value; used when a value stored in a context is expanded
* in a larger context. e.g. [%k (S.t)](k+1) --> [^k]t (t is shifted of k)
*)
let rec shift_value n = function
- | VAL (k,v) -> VAL ((k+n),v)
+ | VAL (k,t) -> VAL (k+n,t)
+ | STACK(k,v,stk) -> STACK(k+n,v,stk)
+ | CBN (t,s) -> CBN(t,subs_shft(n,s))
| LAM (nlams,ctxt,b,s) -> LAM (nlams,ctxt,b,subs_shft (n,s))
| FIXP (fix,s,args) ->
FIXP (fix,subs_shft (n,s), Array.map (shift_value n) args)
@@ -68,6 +94,13 @@ let rec shift_value n = function
let shift_value n v =
if n = 0 then v else shift_value n v
+let rec shift_stack n = function
+ TOP -> TOP
+ | APP(v,stk) -> APP(Array.map (shift_value n) v, shift_stack n stk)
+ | CASE(c,b,i,s,stk) -> CASE(c,b,i,subs_shft(n,s), shift_stack n stk)
+let shift_stack n stk =
+ if n = 0 then stk else shift_stack n stk
+
(* Contracts a fixpoint: given a fixpoint and a bindings,
* returns the corresponding fixpoint body, and the bindings in which
* it should be evaluated: its first variables are the fixpoint bodies
@@ -89,29 +122,6 @@ let make_constr_ref n = function
| VarKey id -> mkVar id
| ConstKey cst -> mkConst cst
-
-(* type of terms with a hole. This hole can appear only under App or Case.
- * TOP means the term is considered without context
- * APP(v,stk) means the term is applied to v, and then the context stk
- * (v.0 is the first argument).
- * this corresponds to the application stack of the KAM.
- * The members of l are values: we evaluate arguments before
- calling the function.
- * CASE(t,br,pat,S,stk) means the term is in a case (which is himself in stk
- * t is the type of the case and br are the branches, all of them under
- * the subs S, pat is information on the patterns of the Case
- * (Weak reduction: we propagate the sub only when the selected branch
- * is determined)
- *
- * Important remark: the APPs should be collapsed:
- * (APP (l,(APP ...))) forbidden
- *)
-
-type cbv_stack =
- | TOP
- | APP of cbv_value array * cbv_stack
- | CASE of constr * constr array * case_info * cbv_value subs * cbv_stack
-
(* Adds an application list. Collapse APPs! *)
let stack_app appl stack =
if Array.length appl = 0 then stack else
@@ -119,6 +129,20 @@ let stack_app appl stack =
| APP(args,stk) -> APP(Array.append appl args,stk)
| _ -> APP(appl, stack)
+let rec stack_concat stk1 stk2 =
+ match stk1 with
+ TOP -> stk2
+ | APP(v,stk1') -> APP(v,stack_concat stk1' stk2)
+ | CASE(c,b,i,s,stk1') -> CASE(c,b,i,s,stack_concat stk1' stk2)
+
+(* merge stacks when there is no shifts in between *)
+let mkSTACK = function
+ v, TOP -> v
+ | STACK(0,v0,stk0), stk -> STACK(0,v0,stack_concat stk0 stk)
+ | v,stk -> STACK(0,v,stk)
+
+
+(* Change: zeta reduction cannot be avoided in CBV *)
open RedFlags
@@ -128,7 +152,8 @@ let red_set_ref flags = function
| ConstKey sp -> red_set flags (fCONST sp)
(* Transfer application lists from a value to the stack
- * useful because fixpoints may be totally applied in several times
+ * useful because fixpoints may be totally applied in several times.
+ * On the other hand, irreductible atoms absorb the full stack.
*)
let strip_appl head stack =
match head with
@@ -148,7 +173,7 @@ let fixp_reducible flgs ((reci,i),_) stk =
CONSTR _ -> true
| _ -> false)
| _ -> false
- else
+ else
false
let cofixp_reducible flgs _ stk =
@@ -156,7 +181,7 @@ let cofixp_reducible flgs _ stk =
match stk with
| (CASE _ | APP(_,CASE _)) -> true
| _ -> false
- else
+ else
false
@@ -196,27 +221,17 @@ let rec norm_head info env t stack =
| Const sp -> norm_head_ref 0 info env stack (ConstKey sp)
- | LetIn (x, b, t, c) ->
+ | LetIn (_, b, _, c) ->
(* zeta means letin are contracted; delta without zeta means we *)
(* allow bindings but leave let's in place *)
- let zeta = red_set (info_flags info) fZETA in
- let env' =
- if zeta
- (* New rule: for Cbv, Delta does not apply to locally bound variables
- or red_set (info_flags info) fDELTA
- *)
- then
- subs_cons ([|cbv_stack_term info TOP env b|],env)
- else
- subs_lift env in
- if zeta then
+ if red_set (info_flags info) fZETA then
+ (* New rule: for Cbv, Delta does not apply to locally bound variables
+ or red_set (info_flags info) fDELTA
+ *)
+ let env' = subs_cons ([|cbv_stack_term info TOP env b|],env) in
norm_head info env' c stack
else
- let normt =
- mkLetIn (x, cbv_norm_term info env b,
- cbv_norm_term info env t,
- cbv_norm_term info env' c) in
- (VAL(0,normt), stack) (* Considérer une coupure commutative ? *)
+ (CBN(t,env), stack) (* Considérer une coupure commutative ? *)
| Evar ev ->
(match evar_value info ev with
@@ -233,23 +248,20 @@ let rec norm_head info env t stack =
(* neutral cases *)
| (Sort _ | Meta _ | Ind _) -> (VAL(0, t), stack)
- | Prod (x,t,c) ->
- (VAL(0, mkProd (x, cbv_norm_term info env t,
- cbv_norm_term info (subs_lift env) c)),
- stack)
+ | Prod _ -> (CBN(t,env), stack)
and norm_head_ref k info env stack normt =
if red_set_ref (info_flags info) normt then
match ref_value_cache info normt with
| Some body -> strip_appl (shift_value k body) stack
- | None -> (VAL(0,make_constr_ref k normt), stack)
- else (VAL(0,make_constr_ref k normt), stack)
+ | None -> (VAL(0,make_constr_ref k normt),stack)
+ else (VAL(0,make_constr_ref k normt),stack)
(* cbv_stack_term performs weak reduction on constr t under the subs
* env, with context stack, i.e. ([env]t stack). First computes weak
* head normal form of t and checks if a redex appears with the stack.
* If so, recursive call to reach the real head normal form. If not,
- * we build a value.
+ * we build a value.
*)
and cbv_stack_term info stack env t =
match norm_head info env t stack with
@@ -268,47 +280,43 @@ and cbv_stack_term info stack env t =
LAM(nlams-nargs,ctxt', b, subs_cons(args,env))
(* a Fix applied enough -> IOTA *)
- | (FIXP(fix,env,_), stk)
+ | (FIXP(fix,env,[||]), stk)
when fixp_reducible (info_flags info) fix stk ->
let (envf,redfix) = contract_fixp env fix in
cbv_stack_term info stk envf redfix
(* constructor guard satisfied or Cofix in a Case -> IOTA *)
- | (COFIXP(cofix,env,_), stk)
+ | (COFIXP(cofix,env,[||]), stk)
when cofixp_reducible (info_flags info) cofix stk->
let (envf,redfix) = contract_cofixp env cofix in
cbv_stack_term info stk envf redfix
(* constructor in a Case -> IOTA *)
- | (CONSTR((sp,n),_), APP(args,CASE(_,br,ci,env,stk)))
+ | (CONSTR((sp,n),[||]), APP(args,CASE(_,br,ci,env,stk)))
when red_set (info_flags info) fIOTA ->
let cargs =
Array.sub args ci.ci_npar (Array.length args - ci.ci_npar) in
cbv_stack_term info (stack_app cargs stk) env br.(n-1)
-
+
(* constructor of arity 0 in a Case -> IOTA *)
| (CONSTR((_,n),_), CASE(_,br,_,env,stk))
when red_set (info_flags info) fIOTA ->
cbv_stack_term info stk env br.(n-1)
- (* may be reduced later by application *)
- | (head, TOP) -> head
- | (FIXP(fix,env,_), APP(appl,TOP)) -> FIXP(fix,env,appl)
- | (COFIXP(cofix,env,_), APP(appl,TOP)) -> COFIXP(cofix,env,appl)
- | (CONSTR(c,_), APP(appl,TOP)) -> CONSTR(c,appl)
-
- (* absurd cases (ill-typed) *)
- | (LAM _, CASE _) -> assert false
+ (* may be reduced later by application *)
+ | (FIXP(fix,env,[||]), APP(appl,TOP)) -> FIXP(fix,env,appl)
+ | (COFIXP(cofix,env,[||]), APP(appl,TOP)) -> COFIXP(cofix,env,appl)
+ | (CONSTR(c,[||]), APP(appl,TOP)) -> CONSTR(c,appl)
(* definitely a value *)
- | (head,stk) -> VAL(0,apply_stack info (cbv_norm_value info head) stk)
+ | (head,stk) -> mkSTACK(head, stk)
(* When we are sure t will never produce a redex with its stack, we
* normalize (even under binders) the applied terms and we build the
* final term
*)
-and apply_stack info t = function
+let rec apply_stack info t = function
| TOP -> t
| APP (args,st) ->
apply_stack info (mkApp(t,Array.map (cbv_norm_value info) args)) st
@@ -318,7 +326,6 @@ and apply_stack info t = function
Array.map (cbv_norm_term info env) br))
st
-
(* performs the reduction on a constr, and returns a constr *)
and cbv_norm_term info env t =
(* reduction under binders *)
@@ -326,7 +333,13 @@ and cbv_norm_term info env t =
(* reduction of a cbv_value to a constr *)
and cbv_norm_value info = function (* reduction under binders *)
- | VAL (n,v) -> lift n v
+ | VAL (n,t) -> lift n t
+ | STACK (0,v,stk) ->
+ apply_stack info (cbv_norm_value info v) stk
+ | STACK (n,v,stk) ->
+ lift n (apply_stack info (cbv_norm_value info v) stk)
+ | CBN(t,env) ->
+ map_constr_with_binders subs_lift (cbv_norm_term info) env t
| LAM (n,ctxt,b,env) ->
let nctxt =
list_map_i (fun i (x,ty) ->
@@ -337,14 +350,14 @@ and cbv_norm_value info = function (* reduction under binders *)
(mkFix (lij,
(names,
Array.map (cbv_norm_term info env) lty,
- Array.map (cbv_norm_term info
+ Array.map (cbv_norm_term info
(subs_liftn (Array.length lty) env)) bds)),
Array.map (cbv_norm_value info) args)
| COFIXP ((j,(names,lty,bds)),env,args) ->
mkApp
(mkCoFix (j,
(names,Array.map (cbv_norm_term info env) lty,
- Array.map (cbv_norm_term info
+ Array.map (cbv_norm_term info
(subs_liftn (Array.length lty) env)) bds)),
Array.map (cbv_norm_value info) args)
| CONSTR (c,args) ->
@@ -354,7 +367,6 @@ and cbv_norm_value info = function (* reduction under binders *)
let cbv_norm infos constr =
with_stats (lazy (cbv_norm_term infos (ESID 0) constr))
-
type cbv_infos = cbv_value infos
(* constant bodies are normalized at the first expansion *)
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-27 12:46:07 +0000