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/** $Id */
package scalac.transformer.matching ;
import scalac.Unit ;
import scalac.ApplicationError ;
import scalac.ast.Tree ;
import scalac.ast.TreeInfo ;
import scalac.util.Name ;
import Tree.* ;
import java.util.* ;
//import scala.compiler.printer.TextTreePrinter ;
//import scala.compiler.printer.XMLAutomPrinter ;
/** a Berry-Sethi style construction for nfas.
* this class plays is the "Builder" for the "Director" class WordRecognizer.
*/
class BerrySethi {
Unit unit;
public BerrySethi(Unit unit) {
this.unit = unit;
}
boolean isStar( Name n ) {
boolean res = TreeInfo.isNameOfStarPattern( n );
//System.out.println("berry-sethi isStar?"+n.toString()+res);
return res;
}
/*
String s = n.toString();
return (s.indexOf("$") != -1)
&&(!s.startsWith("nest"));
}
*/
HashSet labels;
int pos;
// maps a literal pattern to an Integer ( the position )
// is not *really* needed (postfix order determines position!)
HashMap posMap; // pos: Patterns -> Positions
// don't let this fool you, only labelAt is a real, surjective mapping
HashMap labelAt; // chi: Positions -> Obj
TreeSet globalFirst;
// results which hold all info for the NondetWordAutomaton
HashMap follow; // follow: Positions -> Set[Positions]
// Unit test ?
boolean nullable( Tree pat ) {
//System.out.print("<nullable>");
//DEBUG.print( pat );
//System.out.println("</nullable>");
switch( pat ) {
case Apply(_, _):
return false;
case Sequence( Tree[] trees ):
return (trees.length == 0) || nullable( trees );
//case Subsequence( Tree[] trees ):
//return
case Bind(Name n, Tree t):
/*
if( isStar( n ) ) // generated for star/plus(?)
return true;
*/
return nullable( t );
case Alternative(Tree[] choices):
boolean result = false;
for( int i = 0; i < choices.length && !result; i++ )
result = result || nullable( choices[ i ] );
return result;
default:
return false;
}
}
/** returns true if a Sequence pattern matches the empty sequence
* @param pat the sequence pattern.
*/
boolean nullableSequence( Tree pat ) {
switch( pat ) {
case Sequence( Tree[] pats ):
return nullable( pats );
}
return false;
}
/** returns true if a sequence of patterns (usually children of a
* sequence or subsequence node) is nullable.
* @param pats the sequence of patterns
*/
boolean nullable( Tree[] pats ) {
boolean result = true;
for( int i = 0; i < pats.length && result; i++ )
result = result && nullable( pats[ i ] );
return result;
}
/** computes first( alpha ) where alpha is a word regexp
*/
TreeSet compFirst( Tree pat ) {
//System.out.print("<compFirst>");
//DEBUG.print( pat );
//System.out.println("</compFirst>");
switch( pat ) {
case Sequence( Tree[] trees ):
return compFirst( trees );
case Typed(_,_):
case Select(_,_):
case Apply(_, _):
TreeSet tmp = new TreeSet();
tmp.add( (Integer) posMap.get( pat )); // singleton set
return tmp;
case Literal( _ ):
TreeSet tmp = new TreeSet();
tmp.add( (Integer) posMap.get( pat )); // singleton set
return tmp;
//case Subsequence( Tree[] trees ):
//return compFirst( trees );
case Alternative( Tree[] trees ):
TreeSet tmp = new TreeSet();
for( int i = 0; i < trees.length; i++ ) {
tmp.addAll( compFirst( trees[ i ] ));
}
return tmp;
case Bind( _, Tree tree ):
return compFirst( tree );
case Ident( Name name ):
//if( name != Name.fromString("_") )
// throw new ApplicationError("unexpected pattern");
TreeSet tmp = new TreeSet();
tmp.add( (Integer) posMap.get( pat )); // singleton set
return tmp;
default:
throw new ApplicationError("unexpected pattern");
}
}
/** computes last( alpha ) where alpha is a word regexp
*/
TreeSet compLast( Tree pat ) {
//System.out.print("<last>");
//DEBUG.print( pat );
//System.out.println("</compLast>");
switch( pat ) {
case Sequence( _ ):
case Apply(_, _):
TreeSet tmp = new TreeSet();
tmp.add( (Integer) posMap.get( pat )); // singleton set
return tmp;
case Literal( _ ):
TreeSet tmp = new TreeSet();
tmp.add( (Integer) posMap.get( pat )); // singleton set
return tmp;
//case Subsequence( Tree[] trees ):
//return compLast( trees );
case Alternative( Tree[] trees ):
TreeSet tmp = new TreeSet();
for( int i = 0; i < trees.length; i++ ) {
tmp.addAll( compLast( trees ));
}
return tmp;
case Bind( _, Tree tree ):
return compLast( tree );
default:
throw new ApplicationError("unexpected pattern");
}
}
/** computes first(w) where w=alpha_1...alpha_n are successors of a
* sequence node
*/
TreeSet compFirst( Tree[] pats ) {
if( pats.length == 0 )
return new TreeSet();
int i = 0;
Tree tmp = pats[ i ];
TreeSet result = compFirst( tmp );
i++;
while( nullable(tmp) && (i < pats.length )) {
tmp = pats[ i ];
result.addAll( compFirst( tmp ));
i++;
}
return result;
}
// Unit test ?
/** computes last(w) where w are successors of a sequence node
*/
TreeSet compLast( Tree[] pats ) {
/*
System.out.print("<last>");
for( int k = 0; k<pats.length; k++) {
DEBUG.print( pats[k] );
System.out.print(" ");
}
System.out.println();
*/
if( pats.length == 0 )
return new TreeSet();
int i = pats.length - 1;
Tree tmp = pats[ i ];
TreeSet result = compLast( tmp );
i--;
while( nullable(tmp) && (i >= 0 )) {
tmp = pats[ i ];
result.addAll( compLast( tmp ));
i++;
}
return result;
}
// starts from the right-to-left
// precondition: pos is final
// pats are successor patterns of a Sequence node
TreeSet compFollow(Tree[] pats) {
TreeSet first = null;
this.recVars = new HashMap();
TreeSet fol = new TreeSet();
if( pats.length > 0 ) {//non-empty expr
int i = pats.length;
fol.add( new Integer( pos )); // don't modify pos !
do {
--i;
first = compFollow1( fol, pats[ i ] );
if( nullable( pats[ i ] ))
fol.addAll( first );
else
fol = first;
//System.out.println("in compFollow: first"+first);
//System.out.println("in compFollow: fol"+fol);
} while( i > 0 );
}
if( null == first )
first = new TreeSet();
else {
first = fol;
}
this.follow.put(new Integer( 0 ), first);
return first;
}
HashMap recVars;
/** returns the first set of an expression, setting the follow set along
* the way
*/
TreeSet compFollow1( TreeSet fol, Tree pat ) {
//System.out.println("compFollow1("+fol+","+pat+")");
switch( pat ) {
case Sequence( Tree[] trees ):
TreeSet first = null;
int i = trees.length;
if( i > 0 ) { // is nonempty
do {
--i;
first = compFollow1(fol, trees[ i ]);
if( nullable( trees[ i ] ))
fol.addAll( first );
else
fol = first;
} while( i > 0 ) ;
}
if( null == first ) first = new TreeSet();
return first;
case Alternative( Tree[] choices ):
TreeSet first = new TreeSet();
for( int i = choices.length - 1; i >= 0; --i ) {
first.addAll( compFollow1( fol, choices[ i ] ));
}
return first;
case Bind( Name n, Tree t ):
Integer p = (Integer) this.posMap.get( pat );
TreeSet first = compFirst( t );
//System.out.print("BIND" + first);
recVars.put( pat.symbol(), first );
// if( appearsRightmost( n, t ))
// follow = oldfollw + ownfirst
if( isStar( n ) )
fol.addAll( first ); // an iterated pattern
this.follow.put( p, fol.clone() );
//System.out.println("Bind("+n+",...) first:"+first);
//System.out.println("Bind("+n+",...) follow:"+fol);
// continue to compute follow sets with adjusted fol
return compFollow1( fol, t );
case Ident( Name n ):
if ((pat.symbol() != null )
&& pat.symbol().isPrimaryConstructor()) {
// same as Apply
Integer pos = (Integer) this.posMap.get( pat );
TreeSet tset = (TreeSet) fol.clone();
this.follow.put( pos, tset );
TreeSet first = new TreeSet();
first.add( pos );
return first;
}
if ( recVars.keySet().contains( pat.symbol() )) { // grammar
TreeSet first = (TreeSet) recVars.get( pat.symbol() );
TreeSet follow = ((TreeSet) fol.clone());
first.addAll( follow );
//recVars.put//this.follow.put( pat.symbol(), follow );
return first;
}
// --- --- only happens when called from BindingBerrySethi
// [... x ...] changed to [... x@_ ...]
// non-generated, non-recursive variable should not appear,
// so this is a wildcard pattern _
Integer pos = (Integer) this.posMap.get( pat );
TreeSet tset = (TreeSet) fol.clone();
this.follow.put( pos, tset );
TreeSet first = new TreeSet();
first.add( pos );
//System.out.println("Ident("+n+",...) first:"+first);
//System.out.println("Ident("+n+",...) follow:"+tset);
return first;
case Apply(_, _):
case Literal( _ ):
case Typed(_,_):
case Select(_,_):
Integer pos = (Integer) this.posMap.get( pat );
TreeSet tset = (TreeSet) fol.clone();
this.follow.put( pos, tset );
TreeSet first = new TreeSet();
first.add( pos );
return first;
default:
throw new ApplicationError("unexpected pattern: "+pat.getClass());
}
}
/** called at the leaves of the regexp
*/
void seenLabel( Tree pat, Integer i, Label label ) {
this.posMap.put( pat, i );
this.labelAt.put( i, label );
if( label != Label.DefaultLabel ) {
/*
if( this.labels.contains( label ) ) {
switch(label) {
case TreeLabel(Apply(_, Tree[] args)):
if( args.length > 0 ) {
unit.warning(pat.pos, "if this pattern in nondeterminism, it will not compile correctly");
}
}
}
*/
this.labels.add( label );
}
}
/** overriden in BindingBerrySethi
*/
void seenLabel( Tree pat, Label label ) {
seenLabel( pat, new Integer( ++pos ), label );
}
/** returns "Sethi-length" of a pattern, creating the set of position
* along the way
*/
Vector activeBinders;
// todo: replace global variable pos with acc
void traverse( Tree pat ) {
switch( pat ) {
// (is tree automaton stuff, more than Berry-Sethi)
case Apply( _, _ ):
case Typed( _, _ ):
case Select( _, _ ):
Label label = new Label.TreeLabel( pat );
seenLabel( pat, label ) ;
return ;
case Literal( _ ):
Label label = new Label.SimpleLabel( (Literal) pat );
seenLabel( pat, label ) ;
return ;
case Sequence( Tree[] trees ):
for( int i = 0; i < trees.length; i++ ) {
traverse( trees[ i ] );
}
return ;
case Alternative(Tree[] choices):
for( int i = 0; i < choices.length; i++ ) {
traverse( choices[ i ] );
}
return ;
case Bind(Name name, Tree body):
recVars.put( pat.symbol(), Boolean.TRUE );
if( !isStar( name ) )
{
activeBinders.add( pat.symbol() );
traverse( body );
activeBinders.remove( pat.symbol() );
}
else
traverse( body );
return ;
case Ident(Name name):
if ((pat.symbol() != null )
&& pat.symbol().isPrimaryConstructor()) {
// same as Apply
Label label = new Label.TreeLabel( pat );
seenLabel( pat, label ) ;
return ;
}
if( recVars.get( pat.symbol() ) != null ) {
return ;
}
// _ and variable x ( == x @ _ )
Label label = Label.DefaultLabel;
seenLabel( pat, label );
return ;
//else throw new ApplicationError("cannot handle this: "+name);
// case Apply( _, _ ):
//throw new ApplicationError("cannot handle this");
default:
throw new ApplicationError("this is not a pattern");
}
}
TreeMap finals; // final states
//TreeSet initialsRev; // final states
HashMap deltaq[]; // delta
Vector defaultq[]; // default transitions
//HashMap deltaqRev[]; // delta of Rev
//Vector defaultqRev[]; // default transitions of Rev
protected void makeTransition( Integer srcI, Integer destI, Label label ) {
int src = srcI.intValue() ;
int dest = destI.intValue() ;
Vector arrows; //, revArrows;
//Label revLabel = new Label.Pair( srcI, label );
switch( label ) {
case DefaultLabel:
arrows = defaultq[ src ];
//revArrows = defaultqRev[ dest ];
break;
default:
arrows = (Vector) deltaq[ src ].get( label );
if( arrows == null )
deltaq[ src ].put( label,
arrows = new Vector() );
/*
revArrows = (Vector) deltaqRev[ dest ].get( revLabel );
if( revArrows == null )
deltaqRev[ dest ].put( revLabel,
revArrows = new Vector() );
*/
}
arrows.add( destI );
//revArrows.add( srcI );
}
TreeSet initials;
//NondetWordAutom revNfa ;
protected void initialize( Tree[] subexpr ) {
this.posMap = new HashMap();
this.labelAt = new HashMap();
this.follow = new HashMap();
this.labels = new HashSet();
this.recVars = new HashMap();
this.pos = 0;
// determine "Sethi-length" of the regexp
activeBinders = new Vector();
for( int i = 0; i < subexpr.length; i++ ) {
traverse( subexpr[ i ] );
assert ( activeBinders.isEmpty() );
}
this.initials = new TreeSet();
initials.add( new Integer( 0 ));
}
protected void initializeAutom() {
finals = new TreeMap(); // final states
deltaq = new HashMap[ pos ]; // delta
defaultq = new Vector[ pos ]; // default transitions
for( int j = 0; j < pos; j++ ) {
deltaq[ j ] = new HashMap();
defaultq[ j ] = new Vector();
}
}
void collectTransitions() { // make transitions
for( int j = 0; j < pos; j++ ) {
Integer q = new Integer( j );
//System.out.print( "--q="+q );
//System.out.println(" labelAt:"+labelAt.get( q ));
TreeSet fol = (TreeSet) this.follow.get( q );
//assert fol != null;
for( Iterator it = fol.iterator(); it.hasNext(); ) {
Integer p = (Integer) it.next();
//System.out.println( "-- -- p="+p );
if( p.intValue() == pos ) {
finals.put( q, finalTag );
} else {
makeTransition( new Integer(j), p,
(Label) labelAt.get( p ));
}
}
}
}
Integer finalTag;
public NondetWordAutom automatonFrom( Tree pat, Integer finalTag ) {
this.finalTag = finalTag;
//System.out.println( "enter automatonFrom("+pat+","+finalTag+")"); // UNIT TEST
//System.out.println( TextTreePrinter.toString(pat) );
/*DEBUG = new TextTreePrinter( System.out );
DEBUG.begin();
DEBUG.print( pat );
DEBUG.end();
*/
//System.out.println( nullableSequence( pat )); // UNIT TEST
switch( pat ) {
case Sequence( Tree[] subexpr ):
initialize( subexpr );
// (1) compute first
//globalFirst = compFirst( subexpr );
//System.out.println(globalFirst);
// (2) compute follow;
++pos;
//Set ignore = compFollow( subexpr );
//System.out.println(ignore);
//System.exit(0);
//assert (ignore.equals( globalFirst ));
globalFirst = compFollow( subexpr );
//System.out.print("someFirst:");debugPrint(someFirst);
// construct the automaton's explicit representation
initializeAutom();
// defaultqRev = new Vector[ pos ]; // default transitions
collectTransitions();
if( nullable( subexpr )) // initial state is final
finals.put( new Integer(0), finalTag );
//TreeSet initials = new TreeSet();
//initials.add( new Integer( 0 ) );
NondetWordAutom result =
new NondetWordAutom(pos, // = nstates
labels,
initials,
finals,
deltaq,
defaultq,
null/*(Object) qbinders*/);
/*
System.out.println("inBerrySethi");
XMLAutomPrinter pr = new XMLAutomPrinter( System.out );
pr.begin();
pr.print( result );
pr.print( revNfa );
pr.end();
System.out.println("initialsRev = "+initialsRev);
System.out.println("outBerrySethi");
*/
//System.exit(0);
return result; //print();
}
throw new ApplicationError("expected a sequence pattern");
}
void print1() {
System.out.println("after sethi-style processing");
System.out.println("#positions:" + pos);
System.out.println("posMap:");
for( Iterator it = this.posMap.keySet().iterator();
it.hasNext(); ) {
Tree t = (Tree) it.next();
switch(t) {
case Literal( _ ):
System.out.print( "(" + t.toString() + " -> ");
String s2 = ((Integer) posMap.get(t)).toString();
System.out.print( s2 +") ");
}
}
System.out.println("\nfollow: ");
for( int j = 1; j < pos; j++ ) {
TreeSet fol = (TreeSet) this.follow.get(new Integer(j));
System.out.print("("+j+" -> "+fol.toString()+") ");
//debugPrint( fol );
System.out.println();
}
}
}
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