oops3
Class LL1

Object
  Utils
      Visitor
          LL1

All Implemented Interfaces:

Symbols

public class LL1
extends Visitor

ParserFactory aspect: check LL(1). The visitor uses package access.

Each rule and each node needs to be checked for ambiguity: if a node accepts noInput its lookhead must not intersect its follow set.
	Rule	check right-hand side, traverse right-hand side.
	Nonterminal Terminal	nothing to do.
	Sequence	check node, traverse descendants.
	Repeat	if max is not equal to min check node unconditionally (if max equals min, they are both not zero and the lookahead cannot accept noInput; if min is 0, the lookahead accepts empty input and therefore must differ from follow; else there is a variable loop and again lookahead must differ from follow), traverse descendants.
	Delimit	if min is zero, check node (unconditionally) because there might be no loop; if max is not equal to min, check that the lookahead of the delimiter and the follow set of the node do not intersect to detect the end of the loop; also, if the delimiter accepts noInput check that the lookahead of the body and the follow set of the node do not intersect; traverse body and delimiter.
	Xor	check node, traverse descendants.
	And Or	check node unconditionally (there is a loop), traverse descendants.
	AndList OrList	check that the lookahead of the delimiter and the follow set of the node do not intersect to detect the end of the loop (there cannot be noInput); traverse descendants.

Version:

3.3.0

Field Summary

protected Follow	follow follow sets.
protected Parser	parser parser to be checked.

Fields inherited from class Utils

error

Fields inherited from interface Symbols

badInput, endOfFile, firstSymbol, noInput

Constructor Summary

LL1(Parser parser, Follow follow)

Method Summary

protected void	check(Parser.Node node) warning if lookahead and follow intersect.
protected void	check(Parser.Node node, BitSet set) warning if follow and other set intersect.
protected void	checkIf(Parser.Node node) warning if node accepts noInput and lookahead and follow intersect.
boolean	ll1() returns true if LL(1) check succeeds.
Object	visit(Parser.Delimit delimit) check if loop end is detected, traverse body and delimiter.
Object	visit(Parser.Group group) common code: visit descendants.
Object	visit(Parser.Nonterminal nonterminal) nothing to do.
Object	visit(Parser.Permute permute) check node unconditionally, traverse descendants.
Object	visit(Parser.PermutedList permutedList) check node with the delimiter, traverse descendants.
Object	visit(Parser.Repeat repeat) check node unconditionally, traverse decendants.
Object	visit(Parser.Rule rule) check and traverse rhs.
Object	visit(Parser.Sequence sequence) check node, traverse descendants.
Object	visit(Parser.Terminal terminal) nothing to do.
Object	visit(Parser.Xor xor) check node, traverse descendants.

Methods inherited from class Visitor

visit, visit, visit, visit, visit, visit, visit, visit

Methods inherited from class Utils

className, error, error, fromString, getError, message, testScanner, toChars, toString, toString, warning, warning

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

parser

protected final Parser parser

parser to be checked.

follow

protected final Follow follow

follow sets.

Constructor Detail

LL1

public LL1(Parser parser,
           Follow follow)

Method Detail

ll1

public boolean ll1()

returns true if LL(1) check succeeds.

visit

public Object visit(Parser.Rule rule)

check and traverse rhs.

Overrides:

visit in class Visitor

visit

public Object visit(Parser.Terminal terminal)

nothing to do.

Overrides:

visit in class Visitor

visit

public Object visit(Parser.Nonterminal nonterminal)

nothing to do.

Overrides:

visit in class Visitor

visit

public Object visit(Parser.Group group)

common code: visit descendants.

Overrides:

visit in class Visitor

visit

public Object visit(Parser.Sequence sequence)

check node, traverse descendants.

Overrides:

visit in class Visitor

visit

public Object visit(Parser.Repeat repeat)

check node unconditionally, traverse decendants.

Overrides:

visit in class Visitor

visit

public Object visit(Parser.Delimit delimit)

check if loop end is detected, traverse body and delimiter.

Overrides:

visit in class Visitor

visit

public Object visit(Parser.Xor xor)

check node, traverse descendants.

Overrides:

visit in class Visitor

visit

public Object visit(Parser.Permute permute)

check node unconditionally, traverse descendants.

Overrides:

visit in class Visitor

visit

public Object visit(Parser.PermutedList permutedList)

check node with the delimiter, traverse descendants.

Overrides:

visit in class Visitor

checkIf

protected void checkIf(Parser.Node node)

warning if node accepts noInput and lookahead and follow intersect.

check

protected void check(Parser.Node node)

warning if lookahead and follow intersect.

check

protected void check(Parser.Node node,
                     BitSet set)

warning if follow and other set intersect.