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LEXDFA.PAS
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Pascal/Delphi Source File
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1993-01-24
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2KB
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57 lines
unit LexDFA;
(* 2-5-91 AG *)
(* Copyright (c) 1990,91 by Albert Graef, Schillerstr. 18,
6509 Schornsheim/Germany
All rights reserved *)
interface
(* DFA table construction. This code, admittedly, is not the most aesthetic,
but it's quite efficient (and that's the main goal). For further
explanation, refer to Aho/Sethi/Ullman 1986, Section 3.9. *)
procedure makeDFATable;
(* construct DFA from position table *)
implementation
uses LexBase, LexTables;
procedure makeDFATable;
var i : Integer;
begin
(* initialize start states: *)
for i := 2 to 2*n_start_states+1 do
setunion(first_pos_table^[i]^, first_pos_table^[i mod 2]^);
for i := 0 to 2*n_start_states+1 do
act_state := newState(first_pos_table^[i]);
act_state := -1;
while succ(act_state)<n_states do
begin
inc(act_state);
(* add transitions for active state: *)
startStateTrans;
for i := 1 to size(state_table^[act_state].state_pos^) do
with pos_table^[state_table^[act_state].state_pos^[i]] do
if pos_type=char_pos then
addTrans([c], follow_pos)
else if pos_type=cclass_pos then
addTrans(cc^, follow_pos)
else if pos=0 then
state_table^[act_state].final := true;
(* assign next states: *)
for i := state_table^[act_state].trans_lo to n_trans do
with trans_table^[i] do
next_state := addState(follow_pos);
(* merge transitions for the same next state: *)
mergeTrans;
(* sort transitions: *)
sortTrans;
endStateTrans;
end;
end(*makeDFATable*);
end(*LexDFA*).