invariant.ml 24.6 KB
 fpottier committed Mar 01, 2013 1 2 3 4 `````` (* This module discovers information about the shape and content of the stack in each of the automaton's states. *) open Grammar `````` fpottier committed Mar 02, 2013 5 ``````module C = Conflict (* artificial dependency; ensures that [Conflict] runs first *) `````` fpottier committed Mar 01, 2013 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 `````` (* ------------------------------------------------------------------------ *) (* Compute a lower bound on the height of the stack at every state. At the same time, compute which symbols are held in this stack prefix. *) (* In order to compute (a lower bound on) the height of the stack at a state [s], we examine the LR(0) items that compose [s]. For each item, if the bullet is at position [pos], then we can be assured that the height of the stack is at least [pos]. Thus, we compute the maximum of [pos] over all items (of which there is at least one). *) (* The set of items that we use is not closed, but this does not matter; the items that would be added by the closure would not add any information regarding the height of the stack, since the bullet is at position 0 in these items. *) (* Instead of computing just the stack height, we compute, in the same manner, which symbols are on the stack at a state [s]. This is an array of symbols whose length is the height of the stack at [s]. By convention, the top of the stack is the end of the array. *) (* We first compute and tabulate this information at the level of the LR(0) automaton. *) let stack_symbols : Lr0.node -> Symbol.t array = let dummy = `````` POTTIER Francois committed Dec 11, 2014 32 `````` Array.make 0 (Symbol.T Terminal.sharp) `````` fpottier committed Mar 01, 2013 33 34 35 `````` in Misc.tabulate Lr0.n (fun node -> Item.Set.fold (fun item accu -> `````` POTTIER Francois committed Dec 04, 2014 36 `````` let _prod, _nt, rhs, pos, _length = Item.def item in `````` fpottier committed Mar 01, 2013 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 `````` if pos > Array.length accu then Array.sub rhs 0 pos else accu ) (Lr0.items node) dummy ) (* Then, it is easy to extend it to the LR(1) automaton. *) let stack_symbols (node : Lr1.node) : Symbol.t array = stack_symbols (Lr0.core (Lr1.state node)) let stack_height (node : Lr1.node) : int = Array.length (stack_symbols node) (* ------------------------------------------------------------------------ *) (* Above, we have computed a prefix of the stack at every state. We have computed the length of this prefix and the symbols that are held in this prefix of the stack. Now, compute which states may be held in this prefix. *) (* In order to compute this information, we perform an analysis of the automaton, via a least fixed fixed point computation. *) (* It is worth noting that it would be possible to use an analysis based on a least fixed point computation to discover at the same time the length of the stack prefix, the symbols that it contains, and the states that it may contain. This alternate approach, which was used until 2012/08/25, would lead us to discovering a richer invariant, that is, potentially longer prefixes. This extra information, however, was useless; computing it was a waste of time. Hence, as of 2012/08/25, the height of the stack prefix and the symbols that it contains are predicted (see above), and the least fixed computation is used only to populate these prefixes of predictable length with state information. *) (* By the way, this least fixed point analysis remains the most costly computation throughout this module. *) (* Vectors of sets of states. *) module StateVector = struct type property = Lr1.NodeSet.t list let empty = [] let rec equal v1 v2 = match v1, v2 with | [], [] -> true | states1 :: v1, states2 :: v2 -> Lr1.NodeSet.equal states1 states2 && equal v1 v2 | _, _ -> (* Because all heights are known ahead of time, we are able to (and careful to) compare only vectors of equal length. *) assert false let rec join v1 v2 = match v1, v2 with | [], [] -> [] | states1 :: v1, states2 :: v2 -> Lr1.NodeSet.union states1 states2 :: join v1 v2 | _, _ -> (* Because all heights are known ahead of time, we are able to (and careful to) compare only vectors of equal length. *) assert false let push v x = x :: v `````` POTTIER Francois committed Jan 18, 2015 109 110 `````` let truncate = MenhirLib.General.take `````` fpottier committed Mar 01, 2013 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 `````` end (* In order to perform the fixed point computation, we must extend our type of vectors with a bottom element. This element will not appear in the least fixed point, provided every state of the automaton is reachable. *) module StateLattice = struct type property = | Bottom | NonBottom of StateVector.property let bottom = Bottom let empty = NonBottom StateVector.empty let equal v1 v2 = match v1, v2 with | Bottom, Bottom -> true | NonBottom v1, NonBottom v2 -> StateVector.equal v1 v2 | _, _ -> false let join v1 v2 = match v1, v2 with | Bottom, v | v, Bottom -> v | NonBottom v1, NonBottom v2 -> NonBottom (StateVector.join v1 v2) let push v x = match v with | Bottom -> Bottom | NonBottom v -> NonBottom (StateVector.push v x) let truncate h v = match v with | Bottom -> Bottom | NonBottom v -> NonBottom (StateVector.truncate h v) let is_maximal _ = false end open StateLattice (* Define the fixed point. *) let stack_states : Lr1.node -> property = let module F = `````` POTTIER Francois committed Jul 02, 2015 173 174 175 `````` Fix.Make (Maps.PersistentMapsToImperativeMaps(Lr1.NodeMap)) (StateLattice) `````` fpottier committed Mar 01, 2013 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 `````` in F.lfp (fun node (get : Lr1.node -> property) -> (* We use the fact that a state has incoming transitions if and only if it is not a start state. *) match Lr1.incoming_symbol node with | None -> assert (Lr1.predecessors node = []); assert (stack_height node = 0); (* If [node] is a start state, then the stack at [node] may be (in fact, must be) the empty stack. *) empty `````` POTTIER Francois committed Dec 04, 2014 194 `````` | Some _symbol -> `````` fpottier committed Mar 01, 2013 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 `````` (* If [node] is not a start state, then include the contribution of every incoming transition. We compute a join over all predecessors. The contribution of one predecessor is the abstract value found at this predecessor, extended with a new cell for this transition, and truncated to the stack height at [node], so as to avoid obtaining a vector that is longer than expected/necessary. *) let height = stack_height node in List.fold_left (fun v predecessor -> join v (truncate height (push (get predecessor) (Lr1.NodeSet.singleton predecessor)) ) ) bottom (Lr1.predecessors node) ) (* If every state is reachable, then the least fixed point must be non-bottom everywhere, so we may view it as a function that produces a vector of sets of states. *) let stack_states (node : Lr1.node) : StateVector.property = match stack_states node with | Bottom -> (* apparently this node is unreachable *) assert false | NonBottom v -> v (* ------------------------------------------------------------------------ *) (* For each production, compute where (that is, in which states) this production can be reduced. *) let production_where : Lr1.NodeSet.t ProductionMap.t = Lr1.fold (fun accu node -> TerminalMap.fold (fun _ prods accu -> let prod = Misc.single prods in let nodes = try ProductionMap.lookup prod accu with Not_found -> Lr1.NodeSet.empty in ProductionMap.add prod (Lr1.NodeSet.add node nodes) accu ) (Lr1.reductions node) accu ) ProductionMap.empty let production_where (prod : Production.index) : Lr1.NodeSet.t = try (* Production [prod] may be reduced at [nodes]. *) let nodes = ProductionMap.lookup prod production_where in assert (not (Lr1.NodeSet.is_empty nodes)); nodes with Not_found -> (* The production [prod] is never reduced. *) Lr1.NodeSet.empty let ever_reduced prod = not (Lr1.NodeSet.is_empty (production_where prod)) let fold_reduced f prod accu = Lr1.NodeSet.fold f (production_where prod) accu (* ------------------------------------------------------------------------ *) (* Warn about productions that are never reduced. *) let () = let count = ref 0 in Production.iter (fun prod -> if Lr1.NodeSet.is_empty (production_where prod) then match Production.classify prod with | Some nt -> incr count; Error.grammar_warning (Nonterminal.positions nt) `````` 272 `````` "symbol %s is never accepted." (Nonterminal.print false nt) `````` fpottier committed Mar 01, 2013 273 274 275 276 `````` | None -> incr count; Error.grammar_warning (Production.positions prod) `````` 277 `````` "production %sis never reduced." (Production.print prod) `````` fpottier committed Mar 01, 2013 278 279 280 `````` ); if !count > 0 then Error.grammar_warning [] `````` 281 `````` "in total, %d productions are never reduced." !count `````` fpottier committed Mar 01, 2013 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 `````` (* ------------------------------------------------------------------------ *) (* From the above information, deduce, for each production, the states that may appear in the stack when this production is reduced. *) (* We are careful to produce a vector of states whose length is exactly that of the production [prod]. *) let production_states : Production.index -> StateLattice.property = Production.tabulate (fun prod -> let nodes = production_where prod in let height = Production.length prod in Lr1.NodeSet.fold (fun node accu -> join accu (truncate height (NonBottom (stack_states node)) ) ) nodes bottom ) (* ------------------------------------------------------------------------ *) (* We now determine which states must be represented, that is, explicitly pushed onto the stack. For simplicity, a state is either always represented or never represented. More fine-grained strategies, where a single state is sometimes pushed onto the stack and sometimes not pushed, depending on which outgoing transition is being taken, are conceivable, but quite tricky, and probably not worth the trouble. (1) If two states are liable to appear within a single stack cell, then one is represented if and only if the other is represented. This ensures that the structure of stacks is known everywhere and that we can propose types for stacks. (2) If a state [s] has an outgoing transition along nonterminal symbol [nt], and if the [goto] table for symbol [nt] has more than one target, then state [s] is represented. (3) If a stack cell contains more than one state and if at least one of these states is able to handle the [error] token, then these states are represented. (4) If the semantic action associated with a production mentions the [\$syntaxerror] keyword, then the state that is being reduced to (that is, the state that initiated the recognition of this production) is represented. (Indeed, it will be passed as an argument to [errorcase].) *) (* Data. *) let rep : bool UnionFind.point array = Array.init Lr1.n (fun _ -> UnionFind.fresh false) (* Getter. *) let represented state = rep.(Lr1.number state) (* Setters. *) let represent state = UnionFind.change (represented state) true let represents states = represent (Lr1.NodeSet.choose states) (* Enforce condition (1) above. *) let share (v : StateVector.property) = List.iter (fun states -> let dummy = UnionFind.fresh false in Lr1.NodeSet.iter (fun state -> UnionFind.eunion dummy (represented state) ) states ) v let () = Lr1.iter (fun node -> share (stack_states node) ); Production.iter (fun prod -> match production_states prod with | Bottom -> () | NonBottom v -> share v ) (* Enforce condition (2) above. *) let () = Nonterminal.iter (fun nt -> let count = Lr1.targets (fun count _ _ -> count + 1 ) 0 (Symbol.N nt) in if count > 1 then Lr1.targets (fun () sources _ -> List.iter represent sources ) () (Symbol.N nt) ) (* Enforce condition (3) above. *) let handler state = try let _ = SymbolMap.find (Symbol.T Terminal.error) (Lr1.transitions state) in true with Not_found -> try let _ = TerminalMap.lookup Terminal.error (Lr1.reductions state) in true with Not_found -> false let handlers states = Lr1.NodeSet.exists handler states let () = Lr1.iter (fun node -> let v = stack_states node in List.iter (fun states -> if Lr1.NodeSet.cardinal states >= 2 && handlers states then represents states ) v ) (* Enforce condition (4) above. *) let () = Production.iterx (fun prod -> if Action.has_syntaxerror (Production.action prod) then match production_states prod with | Bottom -> () | NonBottom v -> let sites = production_where prod in let length = Production.length prod in if length = 0 then Lr1.NodeSet.iter represent sites else let states = List.nth v (length - 1) in represents states ) (* Define accessors. *) let represented state = UnionFind.find (represented state) let representeds states = if Lr1.NodeSet.is_empty states then assert false else represented (Lr1.NodeSet.choose states) (* Statistics. *) let () = Error.logC 1 (fun f -> let count = Lr1.fold (fun count node -> if represented node then count + 1 else count ) 0 in Printf.fprintf f "%d out of %d states are represented.\n" count Lr1.n ) (* ------------------------------------------------------------------------ *) (* Accessors for information about the stack. *) (* We describe a stack prefix as a list of cells, where each cell is a pair of a symbol and a set of states. The top of the stack is the head of the list. *) type cell = Symbol.t * Lr1.NodeSet.t type word = cell list (* This auxiliary function converts a stack-as-an-array (top of stack at the right end) to a stack-as-a-list (top of stack at list head). *) let convert a = let n = Array.length a in let rec loop i accu = if i = n then accu else loop (i + 1) (a.(i) :: accu) in loop 0 [] (* [stack s] describes the stack when the automaton is in state [s]. *) let stack node : word = List.combine (convert (stack_symbols node)) (stack_states node) (* [prodstack prod] describes the stack when production [prod] is about to be reduced. *) let prodstack prod : word = match production_states prod with | Bottom -> (* This production is never reduced. *) assert false | NonBottom v -> List.combine (convert (Production.rhs prod)) v (* [gotostack nt] is the structure of the stack when a shift transition over nonterminal [nt] is about to be taken. It consists of just one cell. *) let gotostack : Nonterminal.t -> word = Nonterminal.tabulate (fun nt -> let sources = Lr1.targets (fun accu sources _ -> List.fold_right Lr1.NodeSet.add sources accu ) Lr1.NodeSet.empty (Symbol.N nt) in [ Symbol.N nt, sources ] ) let fold f accu w = List.fold_right (fun (symbol, states) accu -> f accu (representeds states) symbol states ) w accu let fold_top f accu w = match w with | [] -> accu | (symbol, states) :: _ -> f (representeds states) symbol `````` POTTIER Francois committed Oct 01, 2015 520 521 522 523 524 525 526 527 ``````let print (w : word) = let b = Buffer.create 64 in fold (fun () _represented symbol _states -> Buffer.add_string b (Symbol.print symbol); Buffer.add_char b ' ' ) () w; Buffer.contents b `````` fpottier committed Mar 01, 2013 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 ``````(* ------------------------------------------------------------------------ *) (* Explain how the stack should be deconstructed when an error is found. We sometimes have a choice as too how many stack cells should be popped. Indeed, several cells in the known suffix of the stack may physically hold a state. If neither of these states handles errors, then we could jump to either. (Indeed, if we jump to one that's nearer, it will in turn pop further stack cells and jump to one that's farther.) In the interests of code size, we should pop as few stack cells as possible. So, we jump to the topmost represented state in the known suffix. *) type state = | Represented | UnRepresented of Lr1.node type instruction = | Die | DownTo of word * state let rewind node : instruction = let w = stack node in let rec rewind w = match w with | [] -> (* I believe that every stack description either is definite (that is, ends with [TailEmpty]) or contains at least one represented state. Thus, if we find an empty [w], this means that the stack is definitely empty. *) Die | ((_, states) as cell) :: w -> if representeds states then (* Here is a represented state. We will pop this cell and no more. *) DownTo ([ cell ], Represented) else if handlers states then begin (* Here is an unrepresented state that can handle errors. The cell must hold a singleton set of states, so we know which state to jump to, even though it isn't represented. *) assert (Lr1.NodeSet.cardinal states = 1); let state = Lr1.NodeSet.choose states in DownTo ([ cell ], UnRepresented state) end else (* Here is an unrepresented state that does not handle errors. Pop this cell and look further. *) match rewind w with | Die -> Die | DownTo (w, st) -> DownTo (cell :: w, st) in rewind w (* ------------------------------------------------------------------------ *) (* We now determine which positions must be kept track of. For simplicity, we do this on a per symbol basis. That is, for each symbol, either we never keep track of position information, or we always do. In fact, we do distinguish start and end positions. This leads to computing two sets of symbols -- those that keep track of their start position and those that keep track of their end position. A symbol on the right-hand side of a production must keep track of its (start or end) position if that position is explicitly requested by a semantic action. Furthermore, if the left-hand symbol of a production must keep track of its start (resp. end) position, then the first (resp. last) symbol of its right-hand side (if there is one) must do so as well. That is, unless the right-hand side is empty. *) open Keyword let startp = ref SymbolSet.empty let endp = ref SymbolSet.empty let rec require where symbol = let wherep = match where with | WhereStart -> startp | WhereEnd -> endp in if not (SymbolSet.mem symbol !wherep) then begin wherep := SymbolSet.add symbol !wherep; match symbol with | Symbol.T _ -> () | Symbol.N nt -> Production.iternt nt (require_aux where) end and require_aux where prod = `````` POTTIER Francois committed Dec 04, 2014 642 `````` let _nt, rhs = Production.def prod in `````` fpottier committed Mar 01, 2013 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 `````` let length = Array.length rhs in if length > 0 then match where with | WhereStart -> require where rhs.(0) | WhereEnd -> require where rhs.(length - 1) let () = Production.iterx (fun prod -> let rhs = Production.rhs prod and ids = Production.identifiers prod and action = Production.action prod in KeywordSet.iter (function | SyntaxError -> () | Position (Left, where, _) -> require_aux where prod | Position (RightNamed id, where, _) -> Array.iteri (fun i id' -> if id = id' then require where rhs.(i) ) ids ) (Action.keywords action) ) let startp = !startp let endp = !endp let () = Error.logC 1 (fun f -> Printf.fprintf f "%d out of %d symbols keep track of their start position.\n\ %d out of %d symbols keep track of their end position.\n" (SymbolSet.cardinal startp) (Terminal.n + Nonterminal.n) (SymbolSet.cardinal endp) (Terminal.n + Nonterminal.n)) let startp symbol = SymbolSet.mem symbol startp let endp symbol = SymbolSet.mem symbol endp (* ------------------------------------------------------------------------- *) (* Miscellaneous. *) let universal symbol = Lr1.fold (fun universal s -> universal && (if represented s then SymbolMap.mem symbol (Lr1.transitions s) else true) ) true (* ------------------------------------------------------------------------ *) (* Discover which states can peek at an error. These are the states `````` POTTIER Francois committed Dec 03, 2014 700 701 `````` where an error token may be on the stream. These are the states that are targets of a reduce action on [error]. *) `````` fpottier committed Mar 01, 2013 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 `````` (* 2012/08/25 I am optimizing this code, whose original version I found had quadratic complexity. The problem is as follows. We can easily iterate over all states to find which states [s] have a reduce action on error. What we must find out, then, is into which state [t] this reduce action takes us. This is not easy to predict, as it depends on the contents of the stack. The original code used an overapproximation, as follows: if the reduction concerns a production whose head symbol is [nt], then all of the states that have an incoming transition labeled [nt] are potential targets. The new version of the code below relies on the same approximation, but uses two successive loops instead of two nested loops. *) let errorpeekers = (* First compute a set of symbols [nt]... *) let nts : SymbolSet.t = Lr1.fold (fun nts node -> try let prods = TerminalMap.lookup Terminal.error (Lr1.reductions node) in let prod = Misc.single prods in let nt = Production.nt prod in SymbolSet.add (Symbol.N nt) nts with Not_found -> nts ) SymbolSet.empty in (* ... then compute the set of all target states of all transitions labeled by some symbol in the set [nt]. *) SymbolSet.fold (fun nt errorpeekers -> Lr1.targets (fun errorpeekers _ target -> Lr1.NodeSet.add target errorpeekers ) errorpeekers nt ) nts Lr1.NodeSet.empty let errorpeeker node = Lr1.NodeSet.mem node errorpeekers (* ------------------------------------------------------------------------ *) (* Here is how we check whether state [s] should have a default reduction. We check whether [s] has no outgoing shift transitions and only has one possible reduction action. In that case, we produce a default reduction action, that is, we perform reduction without consulting the lookahead token. This saves code, but can alter the parser's behavior in the presence of errors. The check for default actions subsumes the check for the case where [s] admits a reduce action with lookahead symbol "#". In that case, it must be the only possible action -- see [Lr1.default_conflict_resolution]. That is, we have reached a point where we have recognized a well-formed input and are now expecting an end-of-stream. In that case, performing reduction without looking at the next token is the right thing to do, since there should in fact be none. The state that we reduce to will also have the same property, and so on, so we will in fact end up rewinding the entire stack and accepting the input when the stack becomes empty. (New as of 2012/01/23.) A state where a shift/reduce conflict was solved in favor of neither (due to a use of the %nonassoc directive) must not perform a default reduction. Indeed, this would effectively mean that the failure that was requested by the user is forgotten and replaced with a reduction. This surprising behavior is present in ocamlyacc and was present in earlier versions of Menhir. See e.g. http://caml.inria.fr/mantis/view.php?id=5462 There is a chance that we might run into trouble if the ideas described in the above two paragraphs collide, that is, if we forbid a default reduction (due to a shift/reduce conflict solved by %nonassoc) in a node where we would like to have default reduction on "#". This situation seems unlikely to arise, so I will not do anything about it for the moment. (Furthermore, someone who uses precedence declarations is looking for trouble anyway.) `````` POTTIER Francois committed Sep 25, 2015 776 777 778 779 780 781 782 `````` Between 2012/05/25 and 2015/09/25, if [--canonical] has been specified, then we disallow default reductions on a normal token, because we do not want to introduce any spurious actions into the automaton. We do still allow default reductions on "#", since they are needed for the automaton to terminate properly. From 2015/09/25 on, we again always allow default reductions, as they seem to be beneficial when explaining syntax errors. *) `````` fpottier committed Mar 01, 2013 783 784 785 786 787 788 789 ``````let (has_default_reduction : Lr1.node -> (Production.index * TerminalSet.t) option), hdrcount = Misc.tabulateo Lr1.number Lr1.fold Lr1.n (fun s -> if Lr1.forbid_default_reduction s then None else `````` POTTIER Francois committed Sep 25, 2015 790 791 792 793 794 795 `````` let reduction = ProductionMap.is_singleton (Lr1.invert (Lr1.reductions s)) in match reduction with | Some _ -> if SymbolMap.purelynonterminal (Lr1.transitions s) then reduction else None `````` fpottier committed Mar 01, 2013 796 `````` | None -> `````` POTTIER Francois committed Sep 25, 2015 797 `````` reduction `````` fpottier committed Mar 01, 2013 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 `````` ) let () = Error.logC 1 (fun f -> Printf.fprintf f "%d out of %d states have a default reduction.\n" hdrcount Lr1.n) (* ------------------------------------------------------------------------ *) let () = Time.tick "Constructing the invariant" (* ------------------------------------------------------------------------ *) (* If any fatal error was signaled up to this point, stop now. This may include errors signaled in the modules [lr1] and [invariant] by calling the function [Error.grammar_warning]. *) let () = if Error.errors() then exit 1 ``````