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Text File  |  2001-06-06  |  2KB  |  73 lines
  1.  
  2. record Token(type,body,line,column)
  3.  
  4. link readll1
  5.  
  6. procedure parseLL1(ll1)
  7. local predictionStack
  8. local x,y,z,top,cur
  9.  predictionStack:=[ll1.start,ll1.eoi]
  10.  cur := scan()
  11. repeat {
  12.     if not(top := pop(predictionStack)) then return
  13.     if top == cur.type then {
  14.         outToken(cur)
  15.         if top == ll1.eoi then break
  16.         cur := scan()
  17.     } else if member(ll1.actions,top) then {
  18.         outAction(top)
  19.     } else if x:=\ll1.sel[top] & y:=\x[cur.type] then {
  20.         every z:=y[*y to 1 by -1] do push(predictionStack,z)
  21.     } else if y:=\ll1.deflt[top] then {
  22.         every z:=y[*y to 1 by -1] do push(predictionStack,z)
  23.     } else {
  24.         #panic mode error recovery
  25.         reportParseError(cur)
  26.         push(predictionStack,top)
  27.         repeat {
  28.            while not member(ll1.fiducials,cur.type) & 
  29.                    cur.type~==ll1.eoi do {
  30.              #write("scanning past ",cur.body)
  31.                cur := scan()
  32.            }
  33.            if x:=!predictionStack &
  34.                (x==cur.type) | 
  35.                member(\ll1.firstFiducials[x], cur.type)
  36.            then break
  37.            else cur := scan()
  38.         }
  39.         repeat {
  40.            top := pop(predictionStack) | 
  41.                stop("system error in panic mode")
  42.             #write("pruning stack ",top)
  43.            if top==cur.type then {
  44.             push(predictionStack,top)
  45.             break
  46.            }
  47.            if member(ll1.actions,top) then {
  48.                outAction(top)
  49.            } else if member(ll1.terminals,top) then {
  50.                outError(top)
  51.            } else if member(\ll1.firstFiducials[top],cur.type)
  52.                    then {
  53.                push(predictionStack,top)
  54.             break
  55.            } else {
  56.                predictionStack := ll1.minLengRHS[top] |||
  57.                         predictionStack
  58.            }
  59.         }
  60.     }
  61. }
  62. return
  63. end
  64. # 
  65. #  Copyright (C) 1994,  T.W. Christopher and G.K. Thiruvathukal.
  66. #  All rights reserved. The use of TLC is governed by conditions
  67. #  similar to GNU Copyleft. Please consult the files distributed
  68. #  with TLC for more information: COPYLEFT, WARRANTY, and README.
  69. #  If the aforementioned files are missing, you can obtain them
  70. #  from {tc,gkt}@iitmax.acc.iit.edu.
  71. # 
  72. # 
  73.