| 1 | (* ML-Yacc Parser Generator (c) 1989 Andrew W. Appel, David R. Tarditi *) |
| 2 | |
| 3 | (* drt (12/15/89) -- the functor should be used during development work, |
| 4 | but it is wastes space in the release version. |
| 5 | |
| 6 | functor ParserGen(structure LrTable : LR_TABLE |
| 7 | structure Stream : STREAM) : LR_PARSER = |
| 8 | *) |
| 9 | |
| 10 | structure LrParser :> LR_PARSER = |
| 11 | struct |
| 12 | val print = fn s => output(std_out,s) |
| 13 | val println = fn s => (print s; print "\n") |
| 14 | structure LrTable = LrTable |
| 15 | structure Stream = Stream |
| 16 | structure Token : TOKEN = |
| 17 | struct |
| 18 | structure LrTable = LrTable |
| 19 | datatype ('a,'b) token = TOKEN of LrTable.term * ('a * 'b * 'b) |
| 20 | val sameToken = fn (TOKEN (t,_),TOKEN(t',_)) => t=t' |
| 21 | end |
| 22 | |
| 23 | |
| 24 | open LrTable |
| 25 | open Token |
| 26 | |
| 27 | val DEBUG = false |
| 28 | exception ParseError |
| 29 | |
| 30 | type ('a,'b) elem = (state * ('a * 'b * 'b)) |
| 31 | type ('a,'b) stack = ('a,'b) elem list |
| 32 | |
| 33 | val showState = fn (STATE s) => ("STATE " ^ (makestring s)) |
| 34 | |
| 35 | fun printStack(stack: ('a,'b) elem list, n: int) = |
| 36 | case stack |
| 37 | of (state, _) :: rest => |
| 38 | (print(" " ^ makestring n ^ ": "); |
| 39 | println(showState state); |
| 40 | printStack(rest, n+1) |
| 41 | ) |
| 42 | | nil => () |
| 43 | |
| 44 | val parse = fn {arg : 'a, |
| 45 | table : LrTable.table, |
| 46 | lexer : ('_b,'_c) token Stream.stream, |
| 47 | saction : int * '_c * ('_b,'_c) stack * 'a -> |
| 48 | nonterm * ('_b * '_c * '_c) * ('_b,'_c) stack, |
| 49 | void : '_b, |
| 50 | ec = {is_keyword,preferred_change, |
| 51 | errtermvalue,showTerminal, |
| 52 | error,terms,noShift}, |
| 53 | lookahead} => |
| 54 | let fun prAction(stack as (state, _) :: _, |
| 55 | next as (TOKEN (term,_),_), action) = |
| 56 | (println "Parse: state stack:"; |
| 57 | printStack(stack, 0); |
| 58 | print(" state=" |
| 59 | ^ showState state |
| 60 | ^ " next=" |
| 61 | ^ showTerminal term |
| 62 | ^ " action=" |
| 63 | ); |
| 64 | case action |
| 65 | of SHIFT s => println ("SHIFT " ^ showState s) |
| 66 | | REDUCE i => println ("REDUCE " ^ (makestring i)) |
| 67 | | ERROR => println "ERROR" |
| 68 | | ACCEPT => println "ACCEPT"; |
| 69 | action) |
| 70 | | prAction (_,_,action) = action |
| 71 | |
| 72 | val action = LrTable.action table |
| 73 | val goto = LrTable.goto table |
| 74 | |
| 75 | fun parseStep(next as (TOKEN (terminal, value as (_,leftPos,_)),lexer) : |
| 76 | ('_b,'_c) token * ('_b,'_c) token Stream.stream, |
| 77 | stack as (state,_) :: _ : ('_b ,'_c) stack) = |
| 78 | case (if DEBUG then prAction(stack, next,action(state, terminal)) |
| 79 | else action(state, terminal)) |
| 80 | of SHIFT s => parseStep(Stream.get lexer, (s,value) :: stack) |
| 81 | | REDUCE i => |
| 82 | let val (nonterm,value,stack as (state,_) :: _ ) = |
| 83 | saction(i,leftPos,stack,arg) |
| 84 | in parseStep(next,(goto(state,nonterm),value)::stack) |
| 85 | end |
| 86 | | ERROR => let val (_,leftPos,rightPos) = value |
| 87 | in error("syntax error\n",leftPos,rightPos); |
| 88 | raise ParseError |
| 89 | end |
| 90 | | ACCEPT => let val (_,(topvalue,_,_)) :: _ = stack |
| 91 | val (token,restLexer) = next |
| 92 | in (topvalue,Stream.cons(token,lexer)) |
| 93 | end |
| 94 | val next as (TOKEN (terminal,(_,leftPos,_)),_) = Stream.get lexer |
| 95 | in parseStep(next,[(initialState table,(void,leftPos,leftPos))]) |
| 96 | end |
| 97 | end; |