CVS: sml-dist/src/ml-yacc/lib parser2.sml, 1.5.12.2, 1.5.12.3
David MacQueen <[email protected]> Tue, 29 Aug 2006 07:05:17 -0700
| Newsgroups | gmane.comp.lang.sml.smlnj.commits |
|---|---|
| Message-ID | <[email protected]> |
Update of /cvsroot/smlnj/sml-dist/src/ml-yacc/lib
In directory sc8-pr-cvs8.sourceforge.net:/tmp/cvs-serv21130/src/ml-yacc/lib
Modified Files:
Tag: primop-branch-2
parser2.sml
Log Message:
minor printing tweaks for debugging lt_inst problem
Index: parser2.sml
===================================================================
RCS file: /cvsroot/smlnj/sml-dist/src/ml-yacc/lib/parser2.sml,v
retrieving revision 1.5.12.2
retrieving revision 1.5.12.3
diff -C2 -d -r1.5.12.2 -r1.5.12.3
*** parser2.sml 28 Aug 2006 22:57:54 -0000 1.5.12.2
--- parser2.sml 29 Aug 2006 14:05:14 -0000 1.5.12.3
***************
*** 1,542 ****
! (* ML-Yacc Parser Generator (c) 1989 Andrew W. Appel, David R. Tarditi *)
!
! (* parser.sml: This is a parser driver for LR tables with an error-recovery
! routine added to it. The routine used is described in detail in this
! article:
!
! 'A Practical Method for LR and LL Syntactic Error Diagnosis and
! Recovery', by M. Burke and G. Fisher, ACM Transactions on
! Programming Langauges and Systems, Vol. 9, No. 2, April 1987,
! pp. 164-197.
!
! This program is an implementation is the partial, deferred method discussed
! in the article. The algorithm and data structures used in the program
! are described below.
!
! This program assumes that all semantic actions are delayed. A semantic
! action should produce a function from unit -> value instead of producing the
! normal value. The parser returns the semantic value on the top of the
! stack when accept is encountered. The user can deconstruct this value
! and apply the unit -> value function in it to get the answer.
!
! It also assumes that the lexer is a lazy stream.
!
! Data Structures:
! ----------------
!
! * The parser:
!
! The state stack has the type
!
! (state * (semantic value * line # * line #)) list
!
! The parser keeps a queue of (state stack * lexer pair). A lexer pair
! consists of a terminal * value pair and a lexer. This allows the
! parser to reconstruct the states for terminals to the left of a
! syntax error, and attempt to make error corrections there.
!
! The queue consists of a pair of lists (x,y). New additions to
! the queue are cons'ed onto y. The first element of x is the top
! of the queue. If x is nil, then y is reversed and used
! in place of x.
!
! Algorithm:
! ----------
!
! * The steady-state parser:
!
! This parser keeps the length of the queue of state stacks at
! a steady state by always removing an element from the front when
! another element is placed on the end.
!
! It has these arguments:
!
! stack: current stack
! queue: value of the queue
! lexPair ((terminal,value),lex stream)
!
! When SHIFT is encountered, the state to shift to and the value are
! are pushed onto the state stack. The state stack and lexPair are
! placed on the queue. The front element of the queue is removed.
!
! When REDUCTION is encountered, the rule is applied to the current
! stack to yield a triple (nonterm,value,new stack). A new
! stack is formed by adding (goto(top state of stack,nonterm),value)
! to the stack.
!
! When ACCEPT is encountered, the top value from the stack and the
! lexer are returned.
!
! When an ERROR is encountered, fixError is called. FixError
! takes the arguments to the parser, fixes the error if possible and
! returns a new set of arguments.
!
! * The distance-parser:
!
! This parser includes an additional argument distance. It pushes
! elements on the queue until it has parsed distance tokens, or an
! ACCEPT or ERROR occurs. It returns a stack, lexer, the number of
! tokens left unparsed, a queue, and an action option.
! *)
!
! signature FIFO =
! sig type 'a queue
! val empty : 'a queue
! exception Empty
! val get : 'a queue -> 'a * 'a queue
! val put : 'a * 'a queue -> 'a queue
! end
!
! (* drt (12/15/89) -- the functor should be used in development work, but
! it wastes space in the release version.
!
! functor ParserGen(structure LrTable : LR_TABLE
! structure Stream : STREAM) : LR_PARSER =
! *)
!
! structure LrParser :> LR_PARSER =
! struct
! structure LrTable = LrTable
! structure Stream = Stream
!
! fun eqT (LrTable.T i, LrTable.T i') = i = i'
!
! structure Token : TOKEN =
! struct
! structure LrTable = LrTable
! datatype ('a,'b) token = TOKEN of LrTable.term * ('a * 'b * 'b)
! val sameToken = fn (TOKEN(t,_),TOKEN(t',_)) => eqT (t,t')
! end
!
! open LrTable
! open Token
!
! val DEBUG1 = false
! val DEBUG2 = false
! exception ParseError
! exception ParseImpossible of int
!
! structure Fifo :> FIFO =
! struct
! type 'a queue = ('a list * 'a list)
! val empty = (nil,nil)
! exception Empty
! fun get(a::x, y) = (a, (x,y))
! | get(nil, nil) = raise Empty
! | get(nil, y) = get(rev y, nil)
! fun put(a,(x,y)) = (x,a::y)
! end
!
! type ('a,'b) elem = (state * ('a * 'b * 'b))
! type ('a,'b) stack = ('a,'b) elem list
! type ('a,'b) lexv = ('a,'b) token
! type ('a,'b) lexpair = ('a,'b) lexv * (('a,'b) lexv Stream.stream)
! type ('a,'b) distanceParse =
! ('a,'b) lexpair *
! ('a,'b) stack *
! (('a,'b) stack * ('a,'b) lexpair) Fifo.queue *
! int ->
! ('a,'b) lexpair *
! ('a,'b) stack *
! (('a,'b) stack * ('a,'b) lexpair) Fifo.queue *
! int *
! action option
!
! type ('a,'b) ecRecord =
! {is_keyword : term -> bool,
! preferred_change : (term list * term list) list,
! error : string * 'b * 'b -> unit,
! errtermvalue : term -> 'a,
! terms : term list,
! showTerminal : term -> string,
! noShift : term -> bool}
!
! local
! val print = fn s => TextIO.output(TextIO.stdOut,s)
! val println = fn s => (print s; print "\n")
! val showState = fn (STATE s) => "STATE " ^ (Int.toString s)
! in
! fun printStack(stack: ('a,'b) stack, n: int) =
! case stack
! of (state,_) :: rest =>
! (print("\t" ^ Int.toString n ^ ": ");
! println(showState state);
! printStack(rest, n+1))
! | nil => ()
!
! fun prAction showTerminal
! (stack as (state,_) :: _, next as (TOKEN (term,_),_), action) =
! (println "Parse: state stack:";
! printStack(stack, 0);
! print(" state="
! ^ showState state
! ^ " next="
! ^ showTerminal term
! ^ " action="
! );
! case action
! of SHIFT state => println ("SHIFT " ^ (showState state))
! | REDUCE i => println ("REDUCE " ^ (Int.toString i))
! | ERROR => println "ERROR"
! | ACCEPT => println "ACCEPT")
! | prAction _ (_,_,action) = ()
! end
!
! (* ssParse: parser which maintains the queue of (state * lexvalues) in a
! steady-state. It takes a table, showTerminal function, saction
! function, and fixError function. It parses until an ACCEPT is
! encountered, or an exception is raised. When an error is encountered,
! fixError is called with the arguments of parseStep (lexv,stack,and
! queue). It returns the lexv, and a new stack and queue adjusted so
! that the lexv can be parsed *)
!
! val ssParse =
! fn (table,showTerminal,saction,fixError,arg) =>
! let val prAction = prAction showTerminal
! val action = LrTable.action table
! val goto = LrTable.goto table
! fun parseStep(args as
! (lexPair as (TOKEN (terminal, value as (_,leftPos,_)),
! lexer
! ),
! stack as (state,_) :: _,
! queue)) =
! let val nextAction = action (state,terminal)
! val _ = if DEBUG1 then prAction(stack,lexPair,nextAction)
! else ()
! in case nextAction
! of SHIFT s =>
! let val newStack = (s,value) :: stack
! val newLexPair = Stream.get lexer
! val (_,newQueue) =Fifo.get(Fifo.put((newStack,newLexPair),
! queue))
! in parseStep(newLexPair,(s,value)::stack,newQueue)
! end
! | REDUCE i =>
! (case saction(i,leftPos,stack,arg)
! of (nonterm,value,stack as (state,_) :: _) =>
! parseStep(lexPair,(goto(state,nonterm),value)::stack,
! queue)
! | _ => raise (ParseImpossible 197))
! | ERROR => parseStep(fixError args)
! | ACCEPT =>
! (case stack
! of (_,(topvalue,_,_)) :: _ =>
! let val (token,restLexer) = lexPair
! in (topvalue,Stream.cons(token,restLexer))
! end
! | _ => raise (ParseImpossible 202))
! end
! | parseStep _ = raise (ParseImpossible 204)
! in parseStep
! end
!
! (* distanceParse: parse until n tokens are shifted, or accept or
! error are encountered. Takes a table, showTerminal function, and
! semantic action function. Returns a parser which takes a lexPair
! (lex result * lexer), a state stack, a queue, and a distance
! (must be > 0) to parse. The parser returns a new lex-value, a stack
! with the nth token shifted on top, a queue, a distance, and action
! option. *)
!
! val distanceParse =
! fn (table,showTerminal,saction,arg) =>
! let val prAction = prAction showTerminal
! val action = LrTable.action table
! val goto = LrTable.goto table
! fun parseStep(lexPair,stack,queue,0) = (lexPair,stack,queue,0,NONE)
! | parseStep(lexPair as (TOKEN (terminal, value as (_,leftPos,_)),
! lexer
! ),
! stack as (state,_) :: _,
! queue,distance) =
! let val nextAction = action(state,terminal)
! val _ = if DEBUG1 then prAction(stack,lexPair,nextAction)
! else ()
! in case nextAction
! of SHIFT s =>
! let val newStack = (s,value) :: stack
! val newLexPair = Stream.get lexer
! in parseStep(newLexPair,(s,value)::stack,
! Fifo.put((newStack,newLexPair),queue),distance-1)
! end
! | REDUCE i =>
! (case saction(i,leftPos,stack,arg)
! of (nonterm,value,stack as (state,_) :: _) =>
! parseStep(lexPair,(goto(state,nonterm),value)::stack,
! queue,distance)
! | _ => raise (ParseImpossible 240))
! | ERROR => (lexPair,stack,queue,distance,SOME nextAction)
! | ACCEPT => (lexPair,stack,queue,distance,SOME nextAction)
! end
! | parseStep _ = raise (ParseImpossible 242)
! in parseStep : ('_a,'_b) distanceParse
! end
!
! (* mkFixError: function to create fixError function which adjusts parser state
! so that parse may continue in the presence of an error *)
!
! fun mkFixError({is_keyword,terms,errtermvalue,
! preferred_change,noShift,
! showTerminal,error,...} : ('_a,'_b) ecRecord,
! distanceParse : ('_a,'_b) distanceParse,
! minAdvance,maxAdvance)
!
! (lexv as (TOKEN (term,value as (_,leftPos,_)),_),stack,queue) =
! let val _ = if DEBUG2 then
! error("syntax error found at " ^ (showTerminal term),
! leftPos,leftPos)
! else ()
!
! fun tokAt(t,p) = TOKEN(t,(errtermvalue t,p,p))
!
! val minDelta = 3
!
! (* pull all the state * lexv elements from the queue *)
!
! val stateList =
! let fun f q = let val (elem,newQueue) = Fifo.get q
! in elem :: (f newQueue)
! end handle Fifo.Empty => nil
! in f queue
! end
!
! (* now number elements of stateList, giving distance from
! error token *)
!
! val (_, numStateList) =
! List.foldr (fn (a,(num,r)) => (num+1,(a,num)::r)) (0, []) stateList
!
! (* Represent the set of potential changes as a linked list.
!
! Values of datatype Change hold information about a potential change.
!
! oper = oper to be applied
! pos = the # of the element in stateList that would be altered.
! distance = the number of tokens beyond the error token which the
! change allows us to parse.
! new = new terminal * value pair at that point
! orig = original terminal * value pair at the point being changed.
! *)
!
! datatype ('a,'b) change = CHANGE of
! {pos : int, distance : int, leftPos: 'b, rightPos: 'b,
! new : ('a,'b) lexv list, orig : ('a,'b) lexv list}
!
!
! val showTerms = concat o map (fn TOKEN(t,_) => " " ^ showTerminal t)
!
! val printChange = fn c =>
! let val CHANGE {distance,new,orig,pos,...} = c
! in (print ("{distance= " ^ (Int.toString distance));
! print (",orig ="); print(showTerms orig);
! print (",new ="); print(showTerms new);
! print (",pos= " ^ (Int.toString pos));
! print "}\n")
! end
!
! val printChangeList = app printChange
!
! (* parse: given a lexPair, a stack, and the distance from the error
! token, return the distance past the error token that we are able to parse.*)
!
! fun parse (lexPair,stack,queuePos : int) =
! case distanceParse(lexPair,stack,Fifo.empty,queuePos+maxAdvance+1)
! of (_,_,_,distance,SOME ACCEPT) =>
! if maxAdvance-distance-1 >= 0
! then maxAdvance
! else maxAdvance-distance-1
! | (_,_,_,distance,_) => maxAdvance - distance - 1
!
! (* catList: concatenate results of scanning list *)
!
! fun catList l f = List.foldr (fn(a,r)=> f a @ r) [] l
!
! fun keywordsDelta new = if List.exists (fn(TOKEN(t,_))=>is_keyword t) new
! then minDelta else 0
!
! fun tryChange{lex,stack,pos,leftPos,rightPos,orig,new} =
! let val lex' = List.foldr (fn (t',p)=>(t',Stream.cons p)) lex new
! val distance = parse(lex',stack,pos+length new-length orig)
! in if distance >= minAdvance + keywordsDelta new
! then [CHANGE{pos=pos,leftPos=leftPos,rightPos=rightPos,
! distance=distance,orig=orig,new=new}]
! else []
! end
!
!
! (* tryDelete: Try to delete n terminals.
! Return single-element [success] or nil.
! Do not delete unshiftable terminals. *)
!
!
! fun tryDelete n ((stack,lexPair as (TOKEN(term,(_,l,r)),_)),qPos) =
! let fun del(0,accum,left,right,lexPair) =
! tryChange{lex=lexPair,stack=stack,
! pos=qPos,leftPos=left,rightPos=right,
! orig=rev accum, new=[]}
! | del(n,accum,left,right,(tok as TOKEN(term,(_,_,r)),lexer)) =
! if noShift term then []
! else del(n-1,tok::accum,left,r,Stream.get lexer)
! in del(n,[],l,r,lexPair)
! end
!
! (* tryInsert: try to insert tokens before the current terminal;
! return a list of the successes *)
!
! fun tryInsert((stack,lexPair as (TOKEN(_,(_,l,_)),_)),queuePos) =
! catList terms (fn t =>
! tryChange{lex=lexPair,stack=stack,
! pos=queuePos,orig=[],new=[tokAt(t,l)],
! leftPos=l,rightPos=l})
!
! (* trySubst: try to substitute tokens for the current terminal;
! return a list of the successes *)
!
! fun trySubst ((stack,lexPair as (orig as TOKEN (term,(_,l,r)),lexer)),
! queuePos) =
! if noShift term then []
! else
! catList terms (fn t =>
! tryChange{lex=Stream.get lexer,stack=stack,
! pos=queuePos,
! leftPos=l,rightPos=r,orig=[orig],
! new=[tokAt(t,r)]})
!
! (* do_delete(toks,lexPair) tries to delete tokens "toks" from "lexPair".
! If it succeeds, returns SOME(toks',l,r,lp), where
! toks' is the actual tokens (with positions and values) deleted,
! (l,r) are the (leftmost,rightmost) position of toks',
! lp is what remains of the stream after deletion
! *)
! fun do_delete(nil,lp as (TOKEN(_,(_,l,_)),_)) = SOME(nil,l,l,lp)
! | do_delete([t],(tok as TOKEN(t',(_,l,r)),lp')) =
! if eqT (t, t')
! then SOME([tok],l,r,Stream.get lp')
! else NONE
! | do_delete(t::rest,(tok as TOKEN(t',(_,l,r)),lp')) =
! if eqT (t,t')
! then case do_delete(rest,Stream.get lp')
! of SOME(deleted,l',r',lp'') =>
! SOME(tok::deleted,l,r',lp'')
! | NONE => NONE
! else NONE
!
! fun tryPreferred((stack,lexPair),queuePos) =
! catList preferred_change (fn (delete,insert) =>
! if List.exists noShift delete then [] (* should give warning at
! parser-generation time *)
! else case do_delete(delete,lexPair)
! of SOME(deleted,l,r,lp) =>
! tryChange{lex=lp,stack=stack,pos=queuePos,
! leftPos=l,rightPos=r,orig=deleted,
! new=map (fn t=>(tokAt(t,r))) insert}
! | NONE => [])
!
! val changes = catList numStateList tryPreferred @
! catList numStateList tryInsert @
! catList numStateList trySubst @
! catList numStateList (tryDelete 1) @
! catList numStateList (tryDelete 2) @
! catList numStateList (tryDelete 3)
!
! val findMaxDist = fn l =>
! foldr (fn (CHANGE {distance,...},high) => Int.max(distance,high)) 0 l
!
! (* maxDist: max distance past error taken that we could parse *)
!
! val maxDist = findMaxDist changes
!
! (* remove changes which did not parse maxDist tokens past the error token *)
!
! val changes = catList changes
! (fn(c as CHANGE{distance,...}) =>
! if distance=maxDist then [c] else [])
!
! in case changes
! of (l as change :: _) =>
! let fun print_msg (CHANGE {new,orig,leftPos,rightPos,...}) =
! let val s =
! case (orig,new)
! of (_::_,[]) => "deleting " ^ (showTerms orig)
! | ([],_::_) => "inserting " ^ (showTerms new)
! | _ => "replacing " ^ (showTerms orig) ^
! " with " ^ (showTerms new)
! in error ("syntax error: " ^ s,leftPos,rightPos)
! end
!
! val _ =
! (if length l > 1 andalso DEBUG2 then
! (print "multiple fixes possible; could fix it by:\n";
! app print_msg l;
! print "chosen correction:\n")
! else ();
! print_msg change)
!
! (* findNth: find nth queue entry from the error
! entry. Returns the Nth queue entry and the portion of
! the queue from the beginning to the nth-1 entry. The
! error entry is at the end of the queue.
!
! Examples:
!
! queue = a b c d e
! findNth 0 = (e,a b c d)
! findNth 1 = (d,a b c)
! *)
!
! val findNth = fn n =>
! let fun f (h::t,0) = (h,rev t)
! | f (h::t,n) = f(t,n-1)
! | f (nil,_) = let exception FindNth
! in raise FindNth
! end
! in f (rev stateList,n)
! end
!
! val CHANGE {pos,orig,new,...} = change
! val (last,queueFront) = findNth pos
! val (stack,lexPair) = last
!
! val lp1 = foldl(fn (_,(_,r)) => Stream.get r) lexPair orig
! val lp2 = foldr(fn(t,r)=>(t,Stream.cons r)) lp1 new
!
! val restQueue =
! Fifo.put((stack,lp2),
! foldl Fifo.put Fifo.empty queueFront)
! val (lexPair,stack,queue,_,_) =
! distanceParse(lp2,stack,restQueue,pos)
! in (lexPair,stack,queue)
! end
! | nil => (error("syntax error found at " ^ (showTerminal term),
! leftPos,leftPos); raise ParseError)
! end
! val parse = fn {arg,table,lexer,saction,void,lookahead,
! ec=ec as {showTerminal,...} : ('_a,'_b) ecRecord} =>
! let val distance = 15 (* defer distance tokens *)
! val minAdvance = 1 (* must parse at least 1 token past error *)
! val maxAdvance = Int.max(lookahead,0)(* max distance for parse check *)
! val lexPair = Stream.get lexer
! val (TOKEN (_,(_,leftPos,_)),_) = lexPair
! val startStack = [(initialState table,(void,leftPos,leftPos))]
! val startQueue = Fifo.put((startStack,lexPair),Fifo.empty)
! val distanceParse = distanceParse(table,showTerminal,saction,arg)
! val fixError = mkFixError(ec,distanceParse,minAdvance,maxAdvance)
! val ssParse = ssParse(table,showTerminal,saction,fixError,arg)
! fun loop (lexPair,stack,queue,_,SOME ACCEPT) =
! ssParse(lexPair,stack,queue)
! | loop (lexPair,stack,queue,0,_) = ssParse(lexPair,stack,queue)
! | loop (lexPair,stack,queue,distance,SOME ERROR) =
! let val (lexPair,stack,queue) = fixError(lexPair,stack,queue)
! in loop (distanceParse(lexPair,stack,queue,distance))
! end
! | loop _ = let exception ParseInternal
! in raise ParseInternal
! end
! in loop (distanceParse(lexPair,startStack,startQueue,distance))
! end
! end;
--- 1,18 ----
! signature FSIG =
! sig
! type 'a q
! val put : 'a * 'a q -> 'a q
! end
! structure F : FSIG =
! struct
! type 'a q = unit * 'a list
! fun put (a, (x,y)) = (x, a::y) (* put: 'a * ('b * 'a list) -> ('b * 'a list) *)
! end
! structure LrParser =
! struct
! fun f (z, q) = F.put(z, q)
+ end
-------------------------------------------------------------------------
Using Tomcat but need to do more? Need to support web services, security?
Get stuff done quickly with pre-integrated technology to make your job easier
Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo
http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642